Heterodimeric antibodies that bind CD3 and tumor antigens

ABSTRACT

The present invention is directed to novel heterodimeric antibodies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/141,350 filed Apr. 28, 2016, which is a continuation-in-part of U.S.patent application Ser. No. 14/952,714, filed Nov. 25, 2015, whichclaims priority under 35 U.S.C. § 119(e) to U.S. Provisional PatentApplication No. 62/085,117, filed Nov. 26, 2014, U.S. Provisional PatentApplication No. 62/084,908, filed Nov. 26, 2014, U.S. Provisional PatentApplication No. 62/085,027, filed Nov. 26, 2014 and U.S. ProvisionalPatent Application No. 62/085,106, filed Nov. 26, 2014. This applicationalso claims priority under 35 U.S.C. § 119(e) to U.S. Provisional PatentApplication No. 62/159,111, filed May 8, 2015, U.S. Provisional PatentApplication No. 62/251,005, filed Nov. 4, 2015 and U.S. ProvisionalPatent Application No. 62/250,971, filed Nov. 4, 2015. U.S. patentapplication Ser. No. 15/141,350 filed Apr. 28, 2016 is also acontinuation-in-part of PCT/US2015/062772, filed Nov. 25, 2015. Allbenefit applications are expressly incorporated herein by reference intheir entirety, with particular reference to the figures, legends andclaims therein.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has beensubmitted electronically in ASCII format and is hereby incorporated byreference in its entirety. Said ASCII copy, created on Apr. 4, 2018, isnamed 067461-5180U503 ST25.txt and is 1,077,152 bytes in size.

BACKGROUND OF THE INVENTION

Antibody-based therapeutics have been used successfully to treat avariety of diseases, including cancer and autoimmune/inflammatorydisorders. Yet improvements to this class of drugs are still needed,particularly with respect to enhancing their clinical efficacy. Oneavenue being explored is the engineering of additional and novel antigenbinding sites into antibody-based drugs such that a singleimmunoglobulin molecule co-engages two different antigens. Suchnon-native or alternate antibody formats that engage two differentantigens are often referred to as bispecifics. Because the considerablediversity of the antibody variable region (Fv) makes it possible toproduce an Fv that recognizes virtually any molecule, the typicalapproach to bispecific generation is the introduction of new variableregions into the antibody.

A number of alternate antibody formats have been explored for bispecifictargeting (Chames & Baty, 2009, mAbs 1[6]:1-9; Holliger & Hudson, 2005,Nature Biotechnology 23[9]:1126-1136; Kontermann, mAbs 4(2):182 (2012),all of which are expressly incorporated herein by reference). Initially,bispecific antibodies were made by fusing two cell lines that eachproduced a single monoclonal antibody (Milstein et al., 1983, Nature305:537-540). Although the resulting hybrid hybridoma or quadroma didproduce bispecific antibodies, they were only a minor population, andextensive purification was required to isolate the desired antibody. Anengineering solution to this was the use of antibody fragments to makebispecifics. Because such fragments lack the complex quaternarystructure of a full length antibody, variable light and heavy chains canbe linked in single genetic constructs. Antibody fragments of manydifferent forms have been generated, including diabodies, single chaindiabodies, tandem scFv's, and Fab2 bispecifics (Chames & Baty, 2009,mAbs 1[6]:1-9; Holliger & Hudson, 2005, Nature Biotechnology23[9]:1126-1136; expressly incorporated herein by reference). Whilethese formats can be expressed at high levels in bacteria and may havefavorable penetration benefits due to their small size, they clearrapidly in vivo and can present manufacturing obstacles related to theirproduction and stability. A principal cause of these drawbacks is thatantibody fragments typically lack the constant region of the antibodywith its associated functional properties, including larger size, highstability, and binding to various Fc receptors and ligands that maintainlong half-life in serum (i.e. the neonatal Fc receptor FcRn) or serve asbinding sites for purification (i.e. protein A and protein G).

More recent work has attempted to address the shortcomings offragment-based bispecifics by engineering dual binding into full lengthantibody-like formats (Wu et al., 2007, Nature Biotechnology25[11]:1290-1297; U.S. Ser. No. 12/477,711; Michaelson et al., 2009,mAbs 1[2]:128-141; PCT/US2008/074693; Zuo et al., 2000, ProteinEngineering 13[5]:361-367; U.S. Ser. No. 09/865,198; Shen et al., 2006,J Biol Chem 281[16]:10706-10714; Lu et al., 2005, J Biol Chem280[20]:19665-19672; PCT/US2005/025472; expressly incorporated herein byreference). These formats overcome some of the obstacles of the antibodyfragment bispecifics, principally because they contain an Fc region. Onesignificant drawback of these formats is that, because they build newantigen binding sites on top of the homodimeric constant chains, bindingto the new antigen is always bivalent.

For many antigens that are attractive as co-targets in a therapeuticbispecific format, the desired binding is monovalent rather thanbivalent. For many immune receptors, cellular activation is accomplishedby cross-linking of a monovalent binding interaction. The mechanism ofcross-linking is typically mediated by antibody/antigen immunecomplexes, or via effector cell to target cell engagement. For example,the low affinity Fc gamma receptors (FcγRs) such as FcγRIIa, FcγRIIb,and FcγRIIIa bind monovalently to the antibody Fc region. Monovalentbinding does not activate cells expressing these FcγRs; however, uponimmune complexation or cell-to-cell contact, receptors are cross-linkedand clustered on the cell surface, leading to activation. For receptorsresponsible for mediating cellular killing, for example FcγRIIIa onnatural killer (NK) cells, receptor cross-linking and cellularactivation occurs when the effector cell engages the target cell in ahighly avid format (Bowles & Weiner, 2005, J Immunol Methods 304:88-99,expressly incorporated by reference). Similarly, on B cells theinhibitory receptor FcγRIIb downregulates B cell activation only when itengages into an immune complex with the cell surface B-cell receptor(BCR), a mechanism that is mediated by immune complexation of solubleIgG's with the same antigen that is recognized by the BCR (Heyman 2003,Immunol Lett 88[2]:157-161; Smith and Clatworthy, 2010, Nature ReviewsImmunology 10:328-343; expressly incorporated by reference). As anotherexample, CD3 activation of T-cells occurs only when its associatedT-cell receptor (TCR) engages antigen-loaded MHC on antigen presentingcells in a highly avid cell-to-cell synapse (Kuhns et al., 2006,Immunity 24:133-139). Indeed nonspecific bivalent cross-linking of CD3using an anti-CD3 antibody elicits a cytokine storm and toxicity(Perruche et al., 2009, J Immunol 183[2]:953-61; Chatenoud & Bluestone,2007, Nature Reviews Immunology 7:622-632; expressly incorporated byreference). Thus for practical clinical use, the preferred mode of CD3co-engagement for redirected killing of targets cells is monovalentbinding that results in activation only upon engagement with theco-engaged target.

CD38, also known as cyclic ADP ribose hydrolase, is a type IItransmembrane glycoprotein with a long C-terminal extracellular domainand a short N-terminal cytoplasmic domain. Among hematopoietic cells, anassortment of functional effects have been ascribed to CD38 mediatedsignaling, including lymphocyte proliferation, cytokine release,regulation of B and myeloid cell development and survival, and inductionof dendritic cell maturation. CD38 is unregulated in many hematopoeiticmalignancies and in cell lines derived from various hematopoieticmalignancies including non-Hodgkin's lymphoma (NHL), Burkitt's lymphoma(BL), multiple myeloma (MM), B chronic lymphocytic leukemia (B-CLL), Band T acute lymphocytic leukemia (ALL), T cell lymphoma (TCL), acutemyeloid leukemia (AML), hairy cell leukemia (HCL), Hodgkin's Lymphoma(HL), and chronic myeloid leukemia (CML). On the other hand, mostprimitive pluripotent stem cells of the hematopoietic system are CD38-.In spite of the recent progress in the discovery and development ofanti-cancer agents, many forms of cancer involving CD38-expressingtumors still have a poor prognosis. Thus, there is a need for improvedmethods for treating such forms of cancer.

B-cell antigen CD19 (CD19, also known as B-cell surface antigen B4,Leu-12) is a human pan-B-cell surface marker that is expressed fromearly stages of pre-B cell development through terminal differentiationinto plasma cells. CD 19 promotes the proliferation and survival ofmature B cells. It associates in a complex with CD21 on the cellsurface. It also associates with CD81 and Leu-13 and potentiates B cellreceptor (BCR) signaling. Together with the BCR, CD19 modulatesintrinsic and antigen receptor-induced signaling thresholds critical forclonal expansion of B cells and humoral immunity. In collaboration withCD21 it links the adaptive and the innate immune system. Uponactivation, the cytoplasmic tail of CD19 becomes phosphorylated whichleads to binding by Src-family kinases and recruitment of PI-3 kinase.It is an attractive immunotherapy target for cancers of lymphoid originsince it is also expressed on the vast majority of NHL cells as well assome leukemias.

A number of antibodies or antibody conjugates that target CD19 have beenevaluated in pre-clinical studies or in clinical trials for thetreatment of cancers. These anti-CD19 antibodies or antibody conjugatesinclude but are not limited to MT-103 (a single-chain bispecificCD19/CD3 antibody; Hoffman et al, 2005 Int J Cancer 115:98-104;Schlereth et al, 2006 Cancer Immunol Immunother 55:503-514), a CD19/CD16diabody (Schlenzka et al, 2004 Anti-cancer Drugs 15:915-919; Kipriyanovet al, 2002 J Immunol 169:137-144), BU12-saporin (Flavell et al, 1995 BrJ Cancer 72:1373-1379), and anti-CD19-idarubicin (Rowland et al, 1993Cancer Immunol Immunother 55:503-514); all expressly incorporated byreference.

CD123, also known as interleukin-3 receptor alpha (IL-3Rα), is expressedon dendritic cells, monocytes, eosinophils and basophils. CD123 is alsoconstitutively expressed by committed hematopoietic stem/progenitorcells, by most of the myeloid lineage (CD13+, CD14+, CD33+, CD15low),and by some CD19+ cells. It is absent from CD3+ cells.

Thus while bispecifics generated from antibody fragments sufferbiophysical and pharmacokinetic hurdles, a drawback of those built withfull length antibody-like formats is that they engage co-target antigensmultivalently in the absence of the primary target antigen, leading tononspecific activation and potentially toxicity. The present inventionsolves this problem by introducing novel bispecific antibodies directedto CD3 and CD38.

BRIEF SUMMARY OF THE INVENTION

Accordingly, in one aspect the present invention provides heterodimericantibodies comprising: a) a first monomer comprising: i) a first heavychain comprising: 1) a first variable heavy domain; 2) a first constantheavy chain comprising a first Fc domain; 3) a scFv comprising a scFvvariable light domain, an scFv linker and a scFv variable heavy domain;wherein said scFv is covalently attached to the C-terminus of said Fcdomain using a domain linker; b) a second monomer comprising a secondheavy chain comprising a second variable heavy domain and a secondconstant heavy chain comprising a second Fc domain; and c) a commonlight chain comprising a variable light domain and a constant lightdomain.

In a further aspect, the invention provides heterodimeric antibodiescomprising: a) a first monomer comprising: i) a first heavy chaincomprising: 1) a first variable heavy domain; 2) a first constant heavydomain comprising a first Fc domain; and 3) a first variable lightdomain, wherein said first variable light domain is covalently attachedto the C-terminus of said first Fc domain using a domain linker; b) asecond monomer comprising: i) a second variable heavy domain; ii) asecond constant heavy domain comprising a second Fc domain; and iii) athird variable heavy domain, wherein said second variable heavy domainis covalently attached to the C-terminus of said second Fc domain usinga domain linker; c) a common light chain comprising a variable lightdomain and a constant light domain.

In an additional aspect, the invention provides heterodimeric antibodiescomprising: a) a first monomer comprising: i) a first heavy chaincomprising: 1) a first variable heavy domain; 2) a first constant heavychain comprising a first CH1 domain and a first Fc domain; 3) a scFvcomprising a scFv variable light domain, an scFv linker and a scFvvariable heavy domain; wherein said scFv is covalently attached betweenthe C-terminus of said CH1 domain and the N-terminus of said first Fcdomain using domain linkers; b) a second monomer comprising a secondheavy chain comprising a second variable heavy domain and a secondconstant heavy chain comprising a second Fc domain; and c) a commonlight chain comprising a variable light domain and a constant lightdomain.

In a further aspect, the invention provides heterodimeric antibodiescomprising: a) a first monomer comprising: i) a first heavy chaincomprising: 1) a first variable heavy domain; 2) a first constant heavydomain comprising a first Fc domain; and 3) a first variable lightdomain, wherein said second variable light domain is covalently attachedbetween the C-terminus of the CH1 domain of said first constant heavydomain and the N-terminus of said first Fc domain using domain linkers;b) a second monomer comprising: i) a second variable heavy domain; ii) asecond constant heavy domain comprising a second Fc domain; and iii) athird variable heavy domain, wherein said second variable heavy domainis covalently attached to the C-terminus of said second Fc domain usinga domain linker; c) a common light chain comprising a variable lightdomain and a constant light domain.

In an additional aspect, the invention provides heterodimeric antibodiescomprising: a) a first monomer comprising: i) a first heavy chaincomprising: 1) a first variable heavy domain; 2) a first constant heavychain comprising a first CH1 domain and a first Fc domain; 3) a scFvcomprising a scFv variable light domain, an scFv linker and a scFvvariable heavy domain; wherein said scFv is covalently attached betweenthe C-terminus of said CH1 domain and the N-terminus of said first Fcdomain using domain linkers; b) a second monomer comprising a second Fcdomain; and c) a light chain comprising a variable light domain and aconstant light domain.

In some aspects, the first and second Fc domains have a set of aminoacid substitutions selected from the group consisting of S364K/E357Q:L368D/K370S; L368D/K370S: S364K; L368E/K370S: S364K; T411T/E360E/Q362E:D401K; L368D/K370S: S364K/E357L and K370S: S364K/E357Q. Furthermore, thevariable heavy domain(s) and the variable light domain(s) bind a firsttarget tumor antigen (TTA), the scFv binds a second TTA or human CD3. Insome embodiments, the TTA is selected from the group consisting of CD19,CD20 and CD123.

In a further aspect, the invention provides anti-CD3 antigen bindingdomains having CDRs and/or the variable domains and/or the scFvsequences depicted in the Figures for H1.32_L1.47, H1.89_L1.47,H1.90_L1.47, H1.33_L.1.47 and H1.31_L1.47. The invention furtherprovides nucleic acid compositions, expression vector compositions andhost cells.

In an additional aspect, the invention provides heterodimeric antibodiescomprising a) a first monomer comprising: i) a first Fc domain; ii) ananti-CD3 scFv comprising a scFv variable light domain, an scFv linkerand a scFv variable heavy domain; wherein said scFv is covalentlyattached to the N-terminus of said Fc domain using a domain linker; b) asecond monomer comprising a heavy chain comprising: i) a heavy variabledomain; and ii) a heavy chain constant domain comprising a second Fcdomain; and c) a light chain comprising a variable light domain and avariable light constant domain; wherein the anti-CD3 scFv is selectedfrom the group consisting of anti-CD3 H1.32_L1.47, anti-CD3 H1.89_L1.47,anti-CD3 H1.90_L1.47 and anti-CD3 H1.33_L1.47. The heavy variable domainand the light variable domain bind a TTA (including, but not limited toCD19, Cd20, CD38 and CD123).

In an additional aspect, the invention provides anti-CD20 antibodybinding domains comprising: a) a variable light domain comprising avlCDR1 having the sequence RASWSVSYIH (SEQ ID NO:426), a vlCDR2 havingthe sequence ATSNLAS (SEQ ID NOS:427 and 436), and a vlCDR3 having thesequence QQWTHNPPT (SEQ ID NO:428); and b) a variable heavy domaincomprises a vhCDR1 having the sequence SYNMH (SEQ ID NOS:422 and 431), avhCDR2 having the sequence AIYPGNGATSYSQKFQG (SEQ ID NO:423) and avhCDR3 having the sequence SYYMGGDWYFDV (SEQ ID NO:424). In someembodiments, the anti-CD20 antibody binding domains have the C2B8_H1.202L1.113 sequences.

In an additional aspect, the invention provides anti-CD20 antibodybinding domains comprising: a) a variable light domain comprising avlCDR1 having the sequence RASSSVSYIH (SEQ ID NO:435), a vlCDR2 havingthe sequence ATSNLAS (SEQ ID NOS:427 and 436), and a vlCDR3 having thesequence QQWTSNPPT (SEQ ID NO:437); and b) a variable heavy domaincomprises a vhCDR1 having the sequence SYNMH (SEQ ID NOS:422 and 431), avhCDR2 having the sequence AIYPGNGDTSYNQKFQG (SEQ ID NO:432) and avhCDR3 having the sequence STYYGGDWYFNV (SEQ ID NO:433).

In some embodiments, the anti-CD20 antibody binding domains have theC2B8_H1L1 sequences.

In an additional aspect, the invention provides heterodimeric antibodiescomprising a) a first monomer comprising: i) a first Fc domain; ii) ananti-CD3 scFv comprising a scFv variable light domain, an scFv linkerand a scFv variable heavy domain; wherein said scFv is covalentlyattached to the N-terminus of said Fc domain using a domain linker; b) asecond monomer comprising a heavy chain comprising: i) a heavy variabledomain; and ii) a heavy chain constant domain comprising a second Fcdomain; and c) a light chain comprising a variable light domain and avariable light constant domain; wherein the variable heavy and lightchains form a C2B8_H1.202_L1.113 or C2B8_H1L1 binding domain.

In an additional aspect, the invention provides heterodimeric antibodiescomprising a) a first monomer comprising: i) a first Fc domain; ii) ananti-CD3 scFv comprising a scFv variable light domain, an scFv linkerand a scFv variable heavy domain; wherein said scFv is covalentlyattached to the N-terminus of said Fc domain using a domain linker; b) asecond monomer comprising a heavy chain comprising: i) a heavy variabledomain; and ii) a heavy chain constant domain comprising a second Fcdomain; and c) a light chain comprising a variable light domain and avariable light constant domain. In this embodiment, the variable domainsbind CD123 and can have the sequences of 7G3_H1.109_L1.47.

In additional aspects, the present invention provides heterodimericantibodies selected from the group consisting of XENP15049, XENP15051;XENP15050, XENP13676, XENP14696, XENP15629, XENP15053, XENP15630,XENP15631, XENP15632, XENP15633, XENP15634, XENP15635, XENP15636,XENP15638, XENP15639, XENP13677, XENP14388, XENP14389, XENP14390,XENP14391, XENP14392, XENP14393, XENP16366, XENP16367, XENP16368,XENP16369, XENP16370, XENP16371, XENP16372, XENP16373, XENP16375,XENP16376, XENP16377, XENP14045 and XENP13928. Nucleic acids, expressionvectors and host cells are all provided as well, in addition to methodsof making these proteins and treating patients with them.

In additional aspects, the present invention provides heterodimericantibodies comprising a set of 6 CDRs (vhCDR1, vhCDR2, vhCDR3, vlCDR1,vlCDR2 and vlCDR3) from the variable regions of one of the antigenbinding domains from a heterodimeric antibody selected from the groupconsisting of XENP15049, XENP15051; XENP15050, XENP13676, XENP14696,XENP15629, XENP15053, XENP15630, XENP15631, XENP15632, XENP15633,XENP15634, XENP15635, XENP15636, XENP15638, XENP15639, XENP13677,XENP14388, XENP14389, XENP14390, XENP14391, XENP14392, XENP14393,XENP16366, XENP16367, XENP16368, XENP16369, XENP16370, XENP16371,XENP16372, XENP16373, XENP16375, XENP16376, XENP16377, XENP14045 andXENP13928. Nucleic acids, expression vectors and host cells are allprovided as well, in addition to methods of making these proteins andtreating patients with them.

In additional aspects, the present invention provides heterodimericantibodies comprising two sets of CDRs, a first set of each of 6 CDRs(vhCDR1, vhCDR2, vhCDR3, vlCDR1, vlCDR2 and vlCDR3) from the variableregions of one of the antigen binding domains and the second set fromthe variable regions of the other, second antigen binding domains of aheterodimeric antibody selected from the group consisting of XENP15049,XENP15051; XENP15050, XENP13676, XENP14696, XENP15629, XENP15053,XENP15630, XENP15631, XENP15632, XENP15633, XENP15634, XENP15635,XENP15636, XENP15638, XENP15639, XENP13677, XENP14388, XENP14389,XENP14390, XENP14391, XENP14392, XENP14393, XENP16366, XENP16367,XENP16368, XENP16369, XENP16370, XENP16371, XENP16372, XENP16373,XENP16375, XENP16376, XENP16377, XENP14045 and XENP13928. Nucleic acids,expression vectors and host cells are all provided as well, in additionto methods of making these proteins and treating patients with them.

In additional aspects, the present invention provides heterodimericantibodies comprising two sets of vh and vl domains, a first set fromthe variable regions of one of the antigen binding domains and thesecond set from the variable regions of the other, second antigenbinding domains of a heterodimeric antibody selected from the groupconsisting of XENP15049, XENP15051; XENP15050, XENP13676, XENP14696,XENP15629, XENP15053, XENP15630, XENP15631, XENP15632, XENP15633,XENP15634, XENP15635, XENP15636, XENP15638, XENP15639, XENP13677,XENP14388, XENP14389, XENP14390, XENP14391, XENP14392, XENP14393,XENP16366, XENP16367, XENP16368, XENP16369, XENP16370, XENP16371,XENP16372, XENP16373, XENP16375, XENP16376, XENP16377, XENP14045 andXENP13928. Nucleic acids, expression vectors and host cells are allprovided as well, in addition to methods of making these proteins andtreating patients with them.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C depict several formats of the present invention. Twoforms of the “bottle opener” format are depicted, one with the anti-CD3antigen binding domain comprising a scFv and the anti-TTA antigenbinding domain comprising a Fab, and one with these reversed. ThemAb-Fv, mAb-scFv, Central-scFv and Central-Fv formats are all shown.While they are depicted as having the anti-CD3 as the scFv, as discussedherein, any Fv sequences can be switched out and combined; that, theanti-CD3 and the anti-TTA domains of the mAb-Fv, mAb-scFv, central-scFvand central-Fv can be switched. In addition, “one-armed” formats, whereone monomer just comprises an Fc domain, are shown, both a one armCentral-scFv and a one arm Central-Fv. A dual scFv format is also shown.

FIG. 2 depicts the sequences of the “High CD3” anti-CD3_H1.30_L1.47construct, including the variable heavy and light domains (CDRsunderlined), as well as the individual vl and vhCDRs, as well as an scFvconstruct with a charged linker (double underlined). As is true of allthe sequences depicted in the Figures, this charged linker may bereplaced by an uncharged linker or a different charged linker, asneeded.

FIG. 3 depicts the sequences of the “High-Int #1” Anti-CD3_H1.32_L1.47construct, including the variable heavy and light domains (CDRsunderlined), as well as the individual vl and vhCDRs, as well as an scFvconstruct with a charged linker (double underlined). As is true of allthe sequences depicted in the Figures, this charged linker may bereplaced by an uncharged linker or a different charged linker, asneeded.

FIG. 4 depicts the sequences of the “High-Int #2” Anti-CD3_H1.89_L1.47construct, including the variable heavy and light domains (CDRsunderlined), as well as the individual vl and vhCDRs, as well as an scFvconstruct with a charged linker (double underlined). As is true of allthe sequences depicted in the Figures, this charged linker may bereplaced by an uncharged linker or a different charged linker, asneeded.

FIG. 5 depicts the sequences of the “High-Int #3” Anti-CD3_H1.90_L1.47construct, including the variable heavy and light domains (CDRsunderlined), as well as the individual vl and vhCDRs, as well as an scFvconstruct with a charged linker (double underlined). As is true of allthe sequences depicted in the Figures, this charged linker may bereplaced by an uncharged linker or a different charged linker, asneeded.

FIG. 6 depicts the sequences of the “Int” Anti-CD3_H1.90_L1.47construct, including the variable heavy and light domains (CDRsunderlined), as well as the individual vl and vhCDRs, as well as an scFvconstruct with a charged linker (double underlined). As is true of allthe sequences depicted in the Figures, this charged linker may bereplaced by an uncharged linker or a different charged linker, asneeded.

FIG. 7 depicts the sequences of the “Low” Anti-CD3_H1.31_L1.47construct, including the variable heavy and light domains (CDRsunderlined), as well as the individual vl and vhCDRs, as well as an scFvconstruct with a charged linker (double underlined). As is true of allthe sequences depicted in the Figures, this charged linker may bereplaced by an uncharged linker or a different charged linker, asneeded.

FIG. 8 depicts the sequences of the High CD38: OKT10_H1.77_L1.24construct, including the variable heavy and light domains (CDRsunderlined), as well as the individual vl and vhCDRs, as well as an scFvconstruct with a charged linker (double underlined).

FIG. 9 depicts the sequences of the intermediate CD38: OKT10_H1L1.24construct, including the variable heavy and light domains (CDRsunderlined), as well as the individual vl and vhCDRs, as well as an scFvconstruct with a charged linker (double underlined).

FIG. 10 depicts the sequences of the Low CD38: OKT10_H1L1 construct,including the variable heavy and light domains (CDRs underlined), aswell as the individual vl and vhCDRs, as well as an scFv construct witha charged linker (double underlined).

FIG. 11 depicts the sequences of XENP15331.

FIG. 12 depicts the sequences of XENP13243.

FIG. 13 depicts the sequences of XENP14702.

FIG. 14 depicts the sequences of XENP15426.

FIG. 15 depicts the sequences of XENP14701.

FIG. 16 depicts the sequence of XENP14703.

FIG. 17 depicts the sequence of XENP13243.

FIG. 18 depicts the sequences of XENP18967.

FIG. 19 depicts the sequences of XENP18971.

FIG. 20 depicts the sequences of XENP18969.

FIG. 21 depicts the sequences of XENP18970.

FIG. 22 depicts the sequences of XENP18972.

FIG. 23 depicts the sequences of XENP18973.

FIG. 24 depicts the sequences of XENP15055.

FIG. 25 depicts the sequences of XENP13544.

FIG. 26 depicts the sequences of XENP13694.

FIG. 27 depicts the sequence of human CD3 ε.

FIG. 28 depicts the full length (SEQ ID NO:130) and extracellular domain(ECD; SEQ ID NO:131) of the human CD38 protein.

FIG. 29A-29E depict useful pairs of heterodimerization variant sets(including skew and pI variants). On FIG. 29E, there are variants forwhich there are no corresponding “monomer 2” variants; these are pIvariants which can be used alone on either monomer, or included on theFab side of a bottle opener, for example, and an appropriate chargedscFv linker can be used on the second monomer that utilizes a scFv asthe second antigen binding domain. Suitable charged linkers are shown inFIGS. 33A and 33B.

FIG. 30 depict a list of isosteric variant antibody constant regions andtheir respective substitutions. pI_(−) indicates lower pI variants,while pI_(+) indicates higher pI variants. These can be optionally andindependently combined with other heterodimerization variants of theinvention (and other variant types as well, as outlined herein).

FIG. 31 depict useful ablation variants that ablate FcγR binding(sometimes referred to as “knock outs” or “KO” variants).

FIG. 32 show two particularly useful embodiments of the invention.

FIGS. 33A and 33B depicts a number of charged scFv linkers that find usein increasing or decreasing the pI of heterodimeric antibodies thatutilize one or more scFv as a component. The (+H) positive linker findsparticular use herein, particularly with anti-CD3 vl and vh sequencesshown herein. A single prior art scFv linker with a single charge isreferenced as “Whitlow”, from Whitlow et al., Protein Engineering6(8):989-995 (1993). It should be noted that this linker was used forreducing aggregation and enhancing proteolytic stability in scFvs.

FIG. 34 depicts a list of engineered heterodimer-skewing Fc variantswith heterodimer yields (determined by HPLC-CIEX) and thermalstabilities (determined by DSC). Not determined thermal stability isdenoted by “n.d.”.

FIG. 35 Expression yields of bispecifics after protein A affinitypurification.

FIG. 36 Cationic exchange purification chromatograms.

FIG. 37 Redirected T cell cytotoxicity assay, 24 h incubation, 10 kRPMI8226 cells, 400 k T cells. Test articles are anti-CD38×anti-CD3bispecifics. Detection was by LDH

FIG. 38 Redirected T cell cytotoxicity assay, 24 h incubation, 10 kRPMI8226 cells, 500 k human PBMCs. Test articles are anti-CD38×anti-CD3bispecifics. Detection was by LDH.

FIG. 39 depicts the sequences of XENP14419,

FIG. 40 depicts the sequences of XENP14420.

FIG. 41 depicts the sequences of XENP14421.

FIG. 42 depicts the sequences of XENP14422.

FIG. 43 depicts the sequences of XENP14423.

FIG. 44 Redirected T cell cytotoxicity assay, 96 h incubation, 40 kRPMI8226 cells, 400 k human PBMC. Test articles are anti-CD38×anti-CD3Fab-scFv-Fcs. Detection was by flow cytometry, specifically thedisappearance of CD38+ cells.

FIG. 45 Further analysis of redirected T cell cytotoxicity assaydescribed in FIG. 1. The first row shows the Mean Fluorescence Intensity(MFI) of activation marker CD69 on CD4+ and CD8+ T cells as detected byflow cytometry. The second row shows the percentage of CD4+ and CD8+ Tcells that are Ki-67+, a measure of cell proliferation. The third rowshows the intracellular Mean Fluorescence Intensity (MFI) of granzyme Binhibitor PI-9 on CD4+ and CD8+ T cells as detected by flow cytometry.

FIG. 46 Design of mouse study to examine anti-tumor activity ofanti-CD38×anti-CD3 Fab-scFv-Fc bispecifics.

FIG. 47 Tumor size measured by IVIS® as a function of time and treatment

FIG. 48 IVIS® bioluminescent images (Day 10)

FIG. 49 Depletion of CD38⁺ cells in cynomolgus monkeys following singledoses of the indicated test articles

FIG. 50 T cell activation measured by CD69 Mean Fluorescence Intensity(MFI) in cynomolgus monkeys, color coding as in FIG. 49.

FIG. 51 Serum levels of IL-6, following single doses of the indicatedtest articles.

FIG. 52 depicts the sequences of XENP15427.

FIG. 53 depicts the sequences of XENP15428.

FIG. 54 depicts the sequences of XENP15429.

FIG. 55 depicts the sequences of XENP15430.

FIG. 56 depicts the sequences of XENP15431.

FIG. 57 depicts the sequences of XENP15432.

FIG. 58 depicts the sequences of XENP15433.

FIG. 59 depicts the sequences of XENP15434.

FIG. 60 depicts the sequences of XENP15435.

FIG. 61 depicts the sequences of XENP15436.

FIG. 62 depicts the sequences of XENP15437.

FIG. 63 depicts the sequences of XENP15438.

FIG. 64 shows binding affinities in a Biacore assay.

FIG. 65 shows the Heterodimer purity during stable pool generation usingvaried Light chain, Fab-Fc, and scFv-Fc ratios.

FIG. 66 Human IgM and IgG2 depletion by anti-CD38×anti-CD3 bispecificsin a huPBMC mouse model.

FIGS. 67A and 67B depicts stability-optimized, humanized anti-CD3variant scFvs. Substitutions are given relative to the H1 L1.4 scFvsequence. Amino acid numbering is Kabat numbering.

FIGS. 68A-68Z Amino acid sequences of stability-optimized, humanizedanti-CD3 variant scFvs. CDRs are underlined. For each heavy chain/lightchain combination, four sequences are listed: (i) scFv with C-terminal6×His tag, (ii) scFv alone, (iii) VH alone, (iv) VL alone.

FIG. 69 Redirected T cell cytotoxicity assay, 24 h incubation, 10 kRPMI8226 cells, 500 k PBMC. Test articles are anti-CD38 (OKT10_H1L1,OKT10_H1.77 L1.24)×anti-CD3 Fab-scFv-Fcs. Detection was by LDH.

FIG. 70 huPBL-SCID Ig-depletion study. Test articles were dosed 8 dafter PBMC engraftment at 0.03, 0.3, or 3 mg/kg. Route of administrationwas intraperitoneal. Blood samples were taken 14 d after PBMCengraftment, processed to serum, and assayed for human IgM and IgG2.

FIG. 71 depicts the sequences of XENP15049.

FIG. 72 depicts the sequences of XENP15051.

FIG. 73 depicts the sequences of XENP15050.

FIG. 74 depicts the sequences of XENP13676.

FIG. 75 depicts the sequences of XENP14696.

FIG. 76 depicts the sequences of XENP15629.

FIG. 77 depicts the sequences of XENP15053.

FIG. 78 depicts the sequences of XENP15630.

FIG. 79 depicts the sequences of XENP15631.

FIG. 80 depicts the sequences of XENP15632.

FIG. 81 depicts the sequences of XENP15633.

FIG. 82 depicts the sequences of XENP15634.

FIG. 83 depicts the sequences of XENP15635.

FIG. 84 depicts the sequences of XENP15636.

FIG. 85 depicts the sequences of XENP15638.

FIG. 86 depicts the sequences of XENP15639.

FIG. 87 depicts the sequences of XENP13677.

FIG. 88 depicts the sequences of XENP14388.

FIG. 89 depicts the sequences of XENP14389.

FIG. 90 depicts the sequences of XENP14390.

FIG. 91 depicts the sequences of XENP14391.

FIG. 92 depicts the sequences of XENP14392.

FIG. 93 depicts the sequences of XENP14393.

FIG. 94 depicts the sequences of XENP16366.

FIG. 95 depicts the sequences of XENP16367

FIG. 96 depicts the sequences of XENP16368.

FIG. 97 depicts the sequences of XENP16369.

FIG. 98 depicts the sequences of XENP16370.

FIG. 99 depicts the sequences of XENP16371.

FIG. 100 depicts the sequences of XENP16372.

FIG. 101 depicts the sequences of XENP16373.

FIG. 102 depicts the sequences of XENP16374.

FIG. 103 depicts the sequences of XENP16375.

FIG. 104 depicts the sequences of XENP16376. The CDRs, vh and vlsequences of the anti-CD20 Fab arm are shown in FIG. 121.

FIG. 105 depicts the sequences of XENP16377.

FIG. 106 depicts the sequences of the CD20 and CD123 antigens.

FIG. 107 Surface plasmon resonance determination of CD3 affinity. Testarticles are anti-CD20 (C2B8_H1.202_L1.113)×anti-CD3 Fab-scFv-Fcs. HumanCD366-Fc (Sino Biological) was covalently bound to the chip surface.Test articles were passed over at 3.125, 12.5, 50, and 200 nM.

FIG. 108 Surface plasmon resonance determination of CD3 affinity. Testarticles are anti-CD20 (C2B8_H1.202_L1.113)×anti-CD3 Fab-scFv-Fcs.Cynomolgus monkey CD3δε-Fc (Sino Biological) was covalently bound to thechip surface. Test articles were passed over at 3.125, 12.5, 50, and 200nM.

FIG. 109 Surface plasmon resonance determination of CD3 affinity. Testarticles are anti-CD20 (C2B8_H1.202_L1.113)×anti-CD3 Fab-scFv-Fcs. HumanCD3δε-Fc (Sino Biological) was covalently bound to the chip surface.Test articles were passed over at 31.25, 125, 500, and 2000 nM.

FIG. 110 Surface plasmon resonance determination of CD3 affinity. Testarticles are anti-CD20 (C2B8_H1.202_L1.113)×anti-CD3 Fab-scFv-Fcs.Cynomolgus monkey CD3δε-Fc (Sino Biological) was covalently bound to thechip surface. Test articles were passed over at 31.25, 125, 500, and2000 nM.

FIG. 111 Surface plasmon resonance determination of CD3 affinity. Testarticles are anti-CD20 (C2B8_H1.202_L1.113)×anti-CD3 Fab-scFv-Fcs.Cynomolgus monkey CD366-Fc (Sino Biological) was covalently bound to thechip surface. Test articles were passed over at 31.25, 125, 500, and2000 nM.

FIG. 112 Redirected T cell cytotoxicity assay, 24 h incubation, 10 kRamos cells, 250 k PBMC. Test articles are anti-CD20(C2B8_H1.202_L1.113)×anti-CD3 Fab-scFv-Fcs. Detection was by LDH.

FIG. 113 Redirected T cell cytotoxicity assay, 24 h incubation, 20 kJeko cells, 200 k PBMC (CD19-depleted). Test articles are anti-CD20(C2B8_H1.202_L1.113)×anti-CD3 Fab-scFv-Fcs. Detection was by flowcytometry, specifically the disappearance of CD19⁺ cells.

FIG. 114 IL-6 production after 24 h for the experiment described in FIG.113.

FIGS. 115A and 115B Redirected T cell cytotoxicity assay, 5 hincubation, 20 k Jeko cells, 500 k PBMC (CD19-depleted). Test articlesare anti-CD20 (C2B8_H1L1)×anti-CD3 Fab-scFv-Fcs. Detection was by flowcytometry, specifically the disappearance of CD19⁺ cells.

FIGS. 116A and 116B Redirected T cell cytotoxicity assay, 24 hincubation, 20 k Jeko cells, 500 k PBMC (CD19-depleted). Test articlesare anti-CD20 (C2B8_H1.202_L1.113)×anti-CD3 Fab-scFv-Fcs. Detection wasby flow cytometry, specifically the disappearance of CD19⁺ cells.

FIG. 117 IL-6 production after 24 h for the experiment described in FIG.113.

FIG. 118 Redirected T cell cytotoxicity assay, 24 h incubation, 10 kRPMI8226 cells, 500 k PBMC. Test articles are anti-CD38 (OKT10_H1L1,OKT10_H1.77_L1.24)×anti-CD3 Fab-scFv-Fcs. Detection was by LDH.

FIG. 119 huPBL-SCID Ig-depletion study. Test articles were dosed 1 and 8d after PBMC engraftment at 5 mg/kg. Route of administration wasintraperitoneal. Blood samples were taken 14 d after PBMC engraftment,processed to serum, and assayed for human IgM and IgG2.

FIG. 120 huPBL-SCID Ig-depletion study. Test articles were dosed 8 dafter PBMC engraftment at 0.03, 0.3, or 3 mg/kg. Route of administrationwas intraperitoneal. Blood samples were taken 14 d after PBMCengraftment, processed to serum, and assayed for human IgM and IgG2.

FIG. 121 depicts the sequences of High CD20 C2B8_H1.202_L1.113. Thecharged linker depicted is (+H), although other charged or unchargedlinkers can be used, such as those depicted in FIGS. 33A and 33B.

FIG. 122 depicts the sequences of Low CD20 C2B8_H1L1. The charged linkerdepicted is (+H), although other charged or uncharged linkers can beused, such as those depicted in FIGS. 33A and 33B.

FIG. 123 depicts the sequences of CD123 7G3_H1.109_L1.57. The chargedlinker depicted is (+H), although other charged or uncharged linkers canbe used, such as those depicted in FIGS. 33A and 33B.

FIG. 124 shows a matrix of possible combinations for the invention. An“A” means that the CDRs of the referenced CD3 sequences can be combinedwith the CDRs of the TTA on the right hand side. That is, the vhCDRsfrom the variable heavy chain CD3 H1.30 sequence and the vhCDRs from thevariable light chain of CD3 L1.57 sequence can be combined with thevhCDRs from the CD38 OKT10 H1.77 sequence and the vhCDRs from theOKT10L1.24 sequence. A “B” means that the CDRs from the CD3 constructscan be combined with the variable heavy and light domains from the TTA.That is, the vhCDRs from the variable heavy chain CD3 H1.30 sequence andthe vhCDRs from the variable light chain of CD3 L1.57 sequence can becombined with the variable heavy domain CD38 OKT10 H1.77 sequence andthe OKT10L1.24 sequence. A “C” is reversed, such that the variable heavydomain and variable light domain from the CD3 sequences are used withthe CDRs of the TTAs. A “D” is where both the variable heavy andvariable light chains from each are combined. An “E” is where the scFvof the CD3 is used with the CDRs of the TTA, and an “F” is where thescFv of the CD3 is used with the variable heavy and variable lightdomains of the TTA antigen binding domain. All of these combinations canbe done in bottle opener formats, for example with any of the backboneformats shown in FIG. 162, or in alternative formats, such as mAb-Fv,mAb-scFv, Central-scFv, Central-Fv or dual scFv formats of FIG. 1,including the format backbones shown in FIGS. 131 and 132). In general,however, formats that would include bivalent binding of CD3 aredisfavored. That is, “A”s (CD3 CDRs X TTA CDRs) can be added to bottleopener sequences (including those of FIG. 162 or inclusive of differentheterodimerization variants) or into a mAb-scFv backbone of FIG. 132, acentral-scFv, a mAb-Fv format or a central-Fv format.

FIG. 125. Schematic of anti-CD123×anti-CD3 Fab-scFv-Fc bispecific.

FIG. 126. Table showing variants engineered to increase affinity andstability of 7G3_H1L1.

FIG. 127. Table showing the properties of final affinity and stabilityoptimized humanized variants of 7G3.

FIG. 128. Binding of XENP14045 (anti-CD123×anti-CD3) bispecific bindingto the CD123 positive AML cell line KG-1a.

FIG. 129. Redirected T cell cytotoxicity (RTCC) of XENP14045 killingKG-1a cells.

FIG. 130. RTCC of XENP14045 with KG-la cells using different ratios ofeffector to target (E:T) cells, demonstrating the “serial killing” by Tcells generated by XENP14045.

FIG. 131. Drug serum levels of 2 mg/kg XENP14045 given IV to C57BL/6mice. The half-life of bispecific was 6.2 days.

FIG. 132. Killing of CD123+ blood basophils and plasmacytoid dendriticcells (PDCs) in cynomolgus monkeys given a single IV dose of 0.01, 0.1,or 1 mg/kg XENP14045.

FIG. 133. Killing of CD123+ basophils and plasmacytoid dendritic cells(PDCs) in the bone marrow of cynomolgus monkeys given a single IV doseof 0.01, 0.1, or 1 mg/kg XENP14045.

FIG. 134. Redistribution of T cells following a single IV dose ofXENP14045 in cynomolgus monkeys.

FIG. 135. CD69 induction of T cells following a single IV dose ofXENP14045 in cynomolgus monkeys.

FIG. 136A-136C. Sequences of the invention. CDR regions are underlined.

FIG. 137. Heterodimer purity during stable pool generation using variedLight chain, Fab-Fc, and scFv-Fc ratios (top). Heterodimer purity ofvarious conditions of pool F2 (bottom).

FIG. 138. SEC showing high purity of XENP14045 cell line material aftertwo-step purification.

FIG. 139 depicts the T cell killing of CD123+ cells.

FIG. 140 depicts the bispecific mechanism to recruit cytotoxic T cellsto kill AML stem cells and blasts.

FIG. 141 depicts the efficient production of the XENP14045 bispecific.

FIG. 142 shows that the XENP14045 bispecific antibody binds to humanAML, with a KD of 8.1 nM to human CD3.

FIG. 143 shows that the XENP14045 bispecific antibody is cross reactivewith primate cells, and has a KD of 5.7 nM to cyno CD3.

FIG. 144 shows that the anti-CD123×anti-CD3 kills human AML cell lines.

FIG. 145 shows that the anti-CD123×anti-CD3 kills human AML cell lines.

FIG. 146 shows the long half life of the bispecific in mice.

FIG. 147 shows the single dose in monkeys.

FIG. 148 shoes the depletion of CD123+ cells in monkeys in bloodbasophiles. Basophil gate, flow cytometry is CD20− CD16+CD14− CD4− CD8−FceR1+.

FIG. 149 shows the depletion in bone marrow basophils, using the samegating.

FIG. 150 shows the repeat dosing that depletes CD123+ cells in monkeys.

FIG. 151 shows the depletion of CD123+ cells in monkeys. Basophil gate,flow cytometry is CD20− CD16+ CD14− CD4− CD8− FceR1+. Plasmoacytoiddendritic cell gate, flow cytometry: CD20− CD16− CD14− Cd4− CD8− CD303+.

FIG. 152 shows depletion in bone marrow in monkeys. Gating as in FIG.151.

FIG. 153 shows the CD123+ cell depletion correlates with T cellredistribution and activation; FIG. 153 is T cell redistribution.

FIG. 154 shows the CD123+ cell depletion correlates with T cellredistribution and activation; FIG. 154 is T cell activation.

FIG. 155 shows the CD123+ cell depletion correlates with T cellredistribution and activation; FIG. 155 is cytokine release.

FIGS. 156A-156D depicts materials associated with the difficulty ofhumanizing anti-CD123 murine sequences as described in Example 3. FIG.125A-C shows the loss of affinity due to the humanization (mainlythrough vH), as 13760 is the Fab of the H0L0 starting murine antibody,with 13763 being the first humanized vH candidate and 13761 having bothhumanized heavy and light Fab chains. FIG. 125D shows the ˜10 fold lossin RTCC potency as a result of the humanization.

FIG. 157 depicts the results of a first round of humanization (“library1”), generating 108 variants, including LDA, targeted and reversionsubstitutions that were affinity screened in a Fab format on a BiacoreCD123 chip, with the stability of neutral and higher affinity variantsscreened on DSF.

FIGS. 158A and 158B shows the increases in Tm as discussed in Example 3.

FIGS. 159A and 159B shows the results of turning the Fabs into a bottleopener format, using a scFv to CD3 and the Fab as developed. FIG. 159Ashows the binding assay and FIG. 159B shows the RTCC assay.

FIGS. 160A-160E show the results from “round 2” of the humanization asoutlined in Example 3. It should be noted that XENP13967 is theequivalent to XENP14045 on the CD123 side; 13967 has a different CD3scFv as shown in the sequences.

FIG. 161 shows the results of the round 2 Tm assay of Example 3.

FIG. 162A-162D shows the sequences of several useful bottle openerformat backbones, without the Fv sequences (e.g. the scFv and the vh andvl for the Fab side). As will be appreciated by those in the art andoutlined below, these sequences can be used with any vh and vl pairsoutlined herein, with one monomer including a scFv (optionally includinga charged scFv linker) and the other monomer including the Fab sequences(e.g. a vh attached to the “Fab side heavy chain” and a vl attached tothe “constant light chain”). The scFv can be anti-CD3 or anti-TTA, withthe Fab being the other. That is, any Fv sequences outlined herein forCD3, CD123, CD38, CD19 or CD20 can be incorporated into these FIG. 162backbones in any combination.

It should be noted that these bottle opener backbones find use in theCentral-scFv format of FIG. 1B, where an additional, second Fab (vh-CH1and vl-constant light) with the same antigen binding as the first Fab isadded to the N-terminus of the scFv on the “bottle opener side”.

FIG. 163 shows the sequence of a mAb-scFv backbone of use in theinvention, to which the Fv sequences of the invention are added. As willbe appreciated by those in the art and outlined below, these sequencescan be used with any vh and vl pairs outlined herein, with one monomerincluding both a Fab and an scFv (optionally including a charged scFvlinker) and the other monomer including the Fab sequence (e.g. a vhattached to the “Fab side heavy chain” and a vl attached to the“constant light chain”). The monomer 1 side is the Fab-scFv pI negativeside, and includes the heterodimerization variants L368D/K370S, theisosteric pI variants N208D/Q295E/N384D/Q418E/N421D, the ablationvariants E233P/L234V/L235A/G236del/S267K, (all relative to IgG1). Themonomer 2 side is the scFv pI positive side, and includes theheterodimerization variants 364K/E357Q. However, other skew variantpairs can be substituted, particularly [S364K/E357Q: L368D/K370S];[L368D/K370S: S364K]; [L368E/K370S: S364K]; [T411T/E360E/Q362E: D401K];[L368D/K370S: S364K/E357L] and [K370S: S364K/E357Q].

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

In order that the application may be more completely understood, severaldefinitions are set forth below. Such definitions are meant to encompassgrammatical equivalents.

By “ablation” herein is meant a decrease or removal of activity. Thusfor example, “ablating FcγR binding” means the Fc region amino acidvariant has less than 50% starting binding as compared to an Fc regionnot containing the specific variant, with less than 70-80-90-95-98% lossof activity being preferred, and in general, with the activity beingbelow the level of detectable binding in a Biacore assay. Of particularuse in the ablation of FcγR binding are those shown in FIG. 16.

By “ADCC” or “antibody dependent cell-mediated cytotoxicity” as usedherein is meant the cell-mediated reaction wherein nonspecific cytotoxiccells that express FcγRs recognize bound antibody on a target cell andsubsequently cause lysis of the target cell. ADCC is correlated withbinding to FcγRIIIa; increased binding to FcγRIIIa leads to an increasein ADCC activity.

By “ADCP” or antibody dependent cell-mediated phagocytosis as usedherein is meant the cell-mediated reaction wherein nonspecific cytotoxiccells that express FcγRs recognize bound antibody on a target cell andsubsequently cause phagocytosis of the target cell.

By “modification” herein is meant an amino acid substitution, insertion,and/or deletion in a polypeptide sequence or an alteration to a moietychemically linked to a protein. For example, a modification may be analtered carbohydrate or PEG structure attached to a protein. By “aminoacid modification” herein is meant an amino acid substitution,insertion, and/or deletion in a polypeptide sequence. For clarity,unless otherwise noted, the amino acid modification is always to anamino acid coded for by DNA, e.g. the 20 amino acids that have codons inDNA and RNA.

By “amino acid substitution” or “substitution” herein is meant thereplacement of an amino acid at a particular position in a parentpolypeptide sequence with a different amino acid. In particular, in someembodiments, the substitution is to an amino acid that is not naturallyoccurring at the particular position, either not naturally occurringwithin the organism or in any organism. For example, the substitutionE272Y refers to a variant polypeptide, in this case an Fc variant, inwhich the glutamic acid at position 272 is replaced with tyrosine. Forclarity, a protein which has been engineered to change the nucleic acidcoding sequence but not change the starting amino acid (for exampleexchanging CGG (encoding arginine) to CGA (still encoding arginine) toincrease host organism expression levels) is not an “amino acidsubstitution”; that is, despite the creation of a new gene encoding thesame protein, if the protein has the same amino acid at the particularposition that it started with, it is not an amino acid substitution.

By “amino acid insertion” or “insertion” as used herein is meant theaddition of an amino acid sequence at a particular position in a parentpolypeptide sequence. For example, −233E or 233E designates an insertionof glutamic acid after position 233 and before position 234.Additionally, −233ADE or A233ADE designates an insertion of AlaAspGluafter position 233 and before position 234.

By “amino acid deletion” or “deletion” as used herein is meant theremoval of an amino acid sequence at a particular position in a parentpolypeptide sequence. For example, E233- or E233# or E233( ) designatesa deletion of glutamic acid at position 233. Additionally, EDA233- orEDA233# designates a deletion of the sequence GluAspAla that begins atposition 233.

By “variant protein” or “protein variant”, or “variant” as used hereinis meant a protein that differs from that of a parent protein by virtueof at least one amino acid modification. Protein variant may refer tothe protein itself, a composition comprising the protein, or the aminosequence that encodes it. Preferably, the protein variant has at leastone amino acid modification compared to the parent protein, e.g. fromabout one to about seventy amino acid modifications, and preferably fromabout one to about five amino acid modifications compared to the parent.As described below, in some embodiments the parent polypeptide, forexample an Fc parent polypeptide, is a human wild type sequence, such asthe Fc region from IgG1, IgG2, IgG3 or IgG4, although human sequenceswith variants can also serve as “parent polypeptides”, for example theIgG1/2 hybrid of FIG. 19. The protein variant sequence herein willpreferably possess at least about 80% identity with a parent proteinsequence, and most preferably at least about 90% identity, morepreferably at least about 95-98-99% identity. Variant protein can referto the variant protein itself, compositions comprising the proteinvariant, or the DNA sequence that encodes it. Accordingly, by “antibodyvariant” or “variant antibody” as used herein is meant an antibody thatdiffers from a parent antibody by virtue of at least one amino acidmodification, “IgG variant” or “variant IgG” as used herein is meant anantibody that differs from a parent IgG (again, in many cases, from ahuman IgG sequence) by virtue of at least one amino acid modification,and “immunoglobulin variant” or “variant immunoglobulin” as used hereinis meant an immunoglobulin sequence that differs from that of a parentimmunoglobulin sequence by virtue of at least one amino acidmodification. “Fc variant” or “variant Fc” as used herein is meant aprotein comprising an amino acid modification in an Fc domain. The Fcvariants of the present invention are defined according to the aminoacid modifications that compose them. Thus, for example, N434S or 434Sis an Fc variant with the substitution serine at position 434 relativeto the parent Fc polypeptide, wherein the numbering is according to theEU index. Likewise, M428L/N434S defines an Fc variant with thesubstitutions M428L and N434S relative to the parent Fc polypeptide. Theidentity of the WT amino acid may be unspecified, in which case theaforementioned variant is referred to as 428L/434S. It is noted that theorder in which substitutions are provided is arbitrary, that is to saythat, for example, 428L/434S is the same Fc variant as M428L/N434S, andso on. For all positions discussed in the present invention that relateto antibodies, unless otherwise noted, amino acid position numbering isaccording to the EU index. The EU index or EU index as in Kabat or EUnumbering scheme refers to the numbering of the EU antibody (Edelman etal., 1969, Proc Natl Acad Sci USA 63:78-85, hereby entirely incorporatedby reference.) The modification can be an addition, deletion, orsubstitution. Substitutions can include naturally occurring amino acidsand, in some cases, synthetic amino acids. Examples include U.S. Pat.No. 6,586,207; WO 98/48032; WO 03/073238; U52004-0214988A1; WO05/35727A2; WO 05/74524A2; J. W. Chin et al., (2002), Journal of theAmerican Chemical Society 124:9026-9027; J. W. Chin, & P. G. Schultz,(2002), ChemBioChem 11:1135-1137; J. W. Chin, et al., (2002), PICASUnited States of America 99:11020-11024; and, L. Wang, & P. G. Schultz,(2002), Chem. 1-10, all entirely incorporated by reference.

As used herein, “protein” herein is meant at least two covalentlyattached amino acids, which includes proteins, polypeptides,oligopeptides and peptides. The peptidyl group may comprise naturallyoccurring amino acids and peptide bonds, or synthetic peptidomimeticstructures, i.e. “analogs”, such as peptoids (see Simon et al., PNAS USA89(20):9367 (1992), entirely incorporated by reference). The amino acidsmay either be naturally occurring or synthetic (e.g. not an amino acidthat is coded for by DNA); as will be appreciated by those in the art.For example, homo-phenylalanine, citrulline, ornithine and noreleucineare considered synthetic amino acids for the purposes of the invention,and both D- and L-(R or S) configured amino acids may be utilized. Thevariants of the present invention may comprise modifications thatinclude the use of synthetic amino acids incorporated using, forexample, the technologies developed by Schultz and colleagues, includingbut not limited to methods described by Cropp & Shultz, 2004, TrendsGenet. 20(12):625-30, Anderson et al., 2004, Proc Natl Acad Sci USA 101(2):7566-71, Zhang et al., 2003, 303(5656):371-3, and Chin et al., 2003,Science 301(5635):964-7, all entirely incorporated by reference. Inaddition, polypeptides may include synthetic derivatization of one ormore side chains or termini, glycosylation, PEGylation, circularpermutation, cyclization, linkers to other molecules, fusion to proteinsor protein domains, and addition of peptide tags or labels.

By “residue” as used herein is meant a position in a protein and itsassociated amino acid identity. For example, Asparagine 297 (alsoreferred to as Asn297 or N297) is a residue at position 297 in the humanantibody IgG1.

By “Fab” or “Fab region” as used herein is meant the polypeptide thatcomprises the VH, CH1, VL, and CL immunoglobulin domains. Fab may referto this region in isolation, or this region in the context of a fulllength antibody, antibody fragment or Fab fusion protein. By “Fv” or “Fvfragment” or “Fv region” as used herein is meant a polypeptide thatcomprises the VL and VH domains of a single antibody. As will beappreciated by those in the art, these generally are made up of twochains.

By “IgG subclass modification” or “isotype modification” as used hereinis meant an amino acid modification that converts one amino acid of oneIgG isotype to the corresponding amino acid in a different, aligned IgGisotype. For example, because IgG1 comprises a tyrosine and IgG2 aphenylalanine at EU position 296, a F296Y substitution in IgG2 isconsidered an IgG subclass modification.

By “non-naturally occurring modification” as used herein is meant anamino acid modification that is not isotypic. For example, because noneof the IgGs comprise a serine at position 434, the substitution 434S inIgG1, IgG2, IgG3, or IgG4 (or hybrids thereof) is considered anon-naturally occurring modification.

By “amino acid” and “amino acid identity” as used herein is meant one ofthe 20 naturally occurring amino acids that are coded for by DNA andRNA.

By “effector function” as used herein is meant a biochemical event thatresults from the interaction of an antibody Fc region with an Fcreceptor or ligand. Effector functions include but are not limited toADCC, ADCP, and CDC.

By “IgG Fc ligand” as used herein is meant a molecule, preferably apolypeptide, from any organism that binds to the Fc region of an IgGantibody to form an Fc/Fc ligand complex. Fc ligands include but are notlimited to FcγRIs, FcγRIIs, FcγRIIIs, FcRn, C1q, C3, mannan bindinglectin, mannose receptor, staphylococcal protein A, streptococcalprotein G, and viral FcγR. Fc ligands also include Fc receptor homologs(FcRH), which are a family of Fc receptors that are homologous to theFcγRs (Davis et al., 2002, Immunological Reviews 190:123-136, entirelyincorporated by reference). Fc ligands may include undiscoveredmolecules that bind Fc. Particular IgG Fc ligands are FcRn and Fc gammareceptors. By “Fc ligand” as used herein is meant a molecule, preferablya polypeptide, from any organism that binds to the Fc region of anantibody to form an Fc/Fc ligand complex.

By “Fc gamma receptor”, “FcγR” or “FcqammaR” as used herein is meant anymember of the family of proteins that bind the IgG antibody Fc regionand is encoded by an FcγR gene. In humans this family includes but isnot limited to FcγRI (CD64), including isoforms FcγRIa, FcγRIb, andFcγRIc; FcγRII (CD32), including isoforms FcγRIIa (including allotypesH131 and R131), FcγRIIb (including FcγRIIb-1 and FcγRIIb-2), andFcγRIIc; and FcγRIII (CD16), including isoforms FcγRIIIa (includingallotypes V158 and F158) and FcγRIIIb (including allotypes FcγRIIb-NA1and FcγRIIb-NA2) (Jefferis et al., 2002, Immunol Lett 82:57-65, entirelyincorporated by reference), as well as any undiscovered human FcγRs orFcγR isoforms or allotypes. An FcγR may be from any organism, includingbut not limited to humans, mice, rats, rabbits, and monkeys. Mouse FcγRsinclude but are not limited to FcγRI (CD64), FcγRII (CD32), FcγRIII(CD16), and FcγRIII-2 (CD16-2), as well as any undiscovered mouse FcγRsor FcγR isoforms or allotypes.

By “FcRn” or “neonatal Fc Receptor” as used herein is meant a proteinthat binds the IgG antibody Fc region and is encoded at least in part byan FcRn gene. The FcRn may be from any organism, including but notlimited to humans, mice, rats, rabbits, and monkeys. As is known in theart, the functional FcRn protein comprises two polypeptides, oftenreferred to as the heavy chain and light chain. The light chain isbeta-2-microglobulin and the heavy chain is encoded by the FcRn gene.Unless otherwise noted herein, FcRn or an FcRn protein refers to thecomplex of FcRn heavy chain with beta-2-microglobulin. A variety of FcRnvariants used to increase binding to the FcRn receptor, and in somecases, to increase serum half-life, are shown in the Figure Legend ofFIG. 83.

By “parent polypeptide” as used herein is meant a starting polypeptidethat is subsequently modified to generate a variant. The parentpolypeptide may be a naturally occurring polypeptide, or a variant orengineered version of a naturally occurring polypeptide. Parentpolypeptide may refer to the polypeptide itself, compositions thatcomprise the parent polypeptide, or the amino acid sequence that encodesit. Accordingly, by “parent immunoglobulin” as used herein is meant anunmodified immunoglobulin polypeptide that is modified to generate avariant, and by “parent antibody” as used herein is meant an unmodifiedantibody that is modified to generate a variant antibody. It should benoted that “parent antibody” includes known commercial, recombinantlyproduced antibodies as outlined below.

By “Fc” or “Fc region” or “Fc domain” as used herein is meant thepolypeptide comprising the constant region of an antibody excluding thefirst constant region immunoglobulin domain and in some cases, part ofthe hinge. Thus Fc refers to the last two constant region immunoglobulindomains of IgA, IgD, and IgG, the last three constant regionimmunoglobulin domains of IgE and IgM, and the flexible hinge N-terminalto these domains. For IgA and IgM, Fc may include the J chain. For IgG,the Fc domain comprises immunoglobulin domains Cy2 and Cy3 (Cy2 and Cy3)and the lower hinge region between Cγ1 (Cγ1) and Cy2 (Cy2). Although theboundaries of the Fc region may vary, the human IgG heavy chain Fcregion is usually defined to include residues C226 or P230 to itscarboxyl-terminus, wherein the numbering is according to the EU index asin Kabat. In some embodiments, as is more fully described below, aminoacid modifications are made to the Fc region, for example to alterbinding to one or more FcγR receptors or to the FcRn receptor.

By “heavy constant region” herein is meant the CH1-hinge-CH2-CH3 portionof an antibody.

By “Fc fusion protein” or “immunoadhesin” herein is meant a proteincomprising an Fc region, generally linked (optionally through a linkermoiety, as described herein) to a different protein, such as a bindingmoiety to a target protein, as described herein. In some cases, onemonomer of the heterodimeric antibody comprises an antibody heavy chain(either including an scFv or further including a light chain) and theother monomer is a Fc fusion, comprising a variant Fc domain and aligand. In some embodiments, these “half antibody-half fusion proteins”are referred to as “Fusionbodies”.

By “position” as used herein is meant a location in the sequence of aprotein. Positions may be numbered sequentially, or according to anestablished format, for example the EU index for antibody numbering.

By “target antigen” as used herein is meant the molecule that is boundspecifically by the variable region of a given antibody. A targetantigen may be a protein, carbohydrate, lipid, or other chemicalcompound. A wide number of suitable target antigens are described below.

By “strandedness” in the context of the monomers of the heterodimericantibodies of the invention herein is meant that, similar to the twostrands of DNA that “match”, heterodimerization variants areincorporated into each monomer so as to preserve the ability to “match”to form heterodimers. For example, if some pI variants are engineeredinto monomer A (e.g. making the pI higher) then steric variants that are“charge pairs” that can be utilized as well do not interfere with the pIvariants, e.g. the charge variants that make a pI higher are put on thesame “strand” or “monomer” to preserve both functionalities. Similarly,for “skew” variants that come in pairs of a set as more fully outlinedbelow, the skilled artisan will consider pI in deciding into whichstrand or monomer that incorporates one set of the pair will go, suchthat pI separation is maximized using the pI of the skews as well.

By “target cell” as used herein is meant a cell that expresses a targetantigen.

By “variable region” as used herein is meant the region of animmunoglobulin that comprises one or more Ig domains substantiallyencoded by any of the V.kappa., V.lamda., and/or VH genes that make upthe kappa, lambda, and heavy chain immunoglobulin genetic locirespectively.

By “wild type or WT” herein is meant an amino acid sequence or anucleotide sequence that is found in nature, including allelicvariations. A WT protein has an amino acid sequence or a nucleotidesequence that has not been intentionally modified.

The antibodies of the present invention are generally isolated orrecombinant. “Isolated,” when used to describe the various polypeptidesdisclosed herein, means a polypeptide that has been identified andseparated and/or recovered from a cell or cell culture from which it wasexpressed. Ordinarily, an isolated polypeptide will be prepared by atleast one purification step. An “isolated antibody,” refers to anantibody which is substantially free of other antibodies havingdifferent antigenic specificities. “Recombinant” means the antibodiesare generated using recombinant nucleic acid techniques in exogeneoushost cells.

“Specific binding” or “specifically binds to” or is “specific for” aparticular antigen or an epitope means binding that is measurablydifferent from a non-specific interaction. Specific binding can bemeasured, for example, by determining binding of a molecule compared tobinding of a control molecule, which generally is a molecule of similarstructure that does not have binding activity. For example, specificbinding can be determined by competition with a control molecule that issimilar to the target.

Specific binding for a particular antigen or an epitope can beexhibited, for example, by an antibody having a KD for an antigen orepitope of at least about 10-4 M, at least about 10-5 M, at least about10-6 M, at least about 10-7 M, at least about 10-8 M, at least about10-9 M, alternatively at least about 10-10 M, at least about 10-11 M, atleast about 10-12 M, or greater, where KD refers to a dissociation rateof a particular antibody-antigen interaction. Typically, an antibodythat specifically binds an antigen will have a KD that is 20-, 50-,100-, 500-, 1000-, 5,000-, 10,000- or more times greater for a controlmolecule relative to the antigen or epitope.

Also, specific binding for a particular antigen or an epitope can beexhibited, for example, by an antibody having a KA or Ka for an antigenor epitope of at least 20-, 50-, 100-, 500-, 1000-, 5,000-, 10,000- ormore times greater for the epitope relative to a control, where KA or Karefers to an association rate of a particular antibody-antigeninteraction. Binding affinity is generally measured using a Biacoreassay.

II. Overview

Bispecific antibodies that co-engage CD3 and a tumor antigen target havebeen designed and used to redirect T cells to attack and lyse targetedtumor cells. Examples include the BiTE and DART formats, whichmonovalently engage CD3 and a tumor antigen. While the CD3-targetingapproach has shown considerable promise, a common side effect of suchtherapies is the associated production of cytokines, often leading totoxic cytokine release syndrome. Because the anti-CD3 binding domain ofthe bispecific antibody engages all T cells, the high cytokine-producingCD4 T cell subset is recruited. Moreover, the CD4 T cell subset includesregulatory T cells, whose recruitment and expansion can potentially leadto immune suppression and have a negative impact on long-term tumorsuppression. In addition, these formats do not contain Fc domains andshow very short serum half-lives in patients.

While the CD3-targeting approach has shown considerable promise, acommon side effect of such therapies is the associated production ofcytokines, often leading to toxic cytokine release syndrome. Because theanti-CD3 binding domain of the bispecific antibody engages all T cells,the high cytokine-producing CD4 T cell subset is recruited. Moreover,the CD4 T cell subset includes regulatory T cells, whose recruitment andexpansion can potentially lead to immune suppression and have a negativeimpact on long-term tumor suppression. One such possible way to reducecytokine production and possibly reduce the activation of CD4 T cells isby reducing the affinity of the anti-CD3 domain for CD3.

Accordingly, in some embodiments the present invention provides antibodyconstructs comprising anti-CD3 antigen binding domains that are “strong”or “high affinity” binders to CD3 (e.g. one example are heavy and lightvariable domains depicted as H1.30_L1.47 (optionally including a chargedlinker as appropriate)) and also bind to CD38. In other embodiments, thepresent invention provides antibody constructs comprising anti-CD3antigen binding domains that are “lite” or “lower affinity” binders toCD3. Additional embodiments provides antibody constructs comprisinganti-CD3 antigen binding domains that have intermediate or “medium”affinity to CD3 that also bind to CD38. Affinity is generally measuredusing a Biacore assay.

It should be appreciated that the “high, medium, low” anti-CD3 sequencesof the present invention can be used in a variety of heterodimerizationformats. While the majority of the disclosure herein uses the “bottleopener” format of heterodimers, these variable heavy and lightsequences, as well as the scFv sequences (and Fab sequences comprisingthese variable heavy and light sequences) can be used in other formats,such as those depicted in FIG. 2 of WO Publication No. 2014/145806, theFigures, formats and legend of which is expressly incorporated herein byreference.

Accordingly, the present invention provides heterodimeric antibodiesthat bind to two different antigens, e.g. the antibodies are“bispecific”, in that they bind two different target antigens, generallytarget tumor antigens (TTAs) as described below. These heterodimericantibodies can bind these target antigens either monovalently (e.g.there is a single antigen binding domain such as a variable heavy andvariable light domain pair) or bivalently (there are two antigen bindingdomains that each independently bind the antigen). The heterodimericantibodies of the invention are based on the use different monomerswhich contain amino acid substitutions that “skew” formation ofheterodimers over homodimers, as is more fully outlined below, coupledwith “pI variants” that allow simple purification of the heterodimersaway from the homodimers, as is similarly outlined below. For theheterodimeric bispecific antibodies of the invention, the presentinvention generally relies on the use of engineered or variant Fcdomains that can self-assemble in production cells to produceheterodimeric proteins, and methods to generate and purify suchheterodimeric proteins.

III. Antibodies

The present invention relates to the generation of bispecific antibodiesthat bind two different antigens, e.g. CD3 and a target tumor antigensuch as CD19, CD20, CD38 and CD123, and are generally therapeuticantibodies. As is discussed below, the term “antibody” is usedgenerally. Antibodies that find use in the present invention can take ona number of formats as described herein, including traditionalantibodies as well as antibody derivatives, fragments and mimetics,described herein.

Traditional antibody structural units typically comprise a tetramer.Each tetramer is typically composed of two identical pairs ofpolypeptide chains, each pair having one “light” (typically having amolecular weight of about 25 kDa) and one “heavy” chain (typicallyhaving a molecular weight of about 50-70 kDa). Human light chains areclassified as kappa and lambda light chains. The present invention isdirected to the IgG class, which has several subclasses, including, butnot limited to IgG1, IgG2, IgG3, and IgG4. It should be noted that IgG1has different allotypes with polymorphisms at 356 (D or E) and 358 (L orM). The sequences depicted herein use the 356D/358M allotype, howeverthe other allotype is included herein. That is, any sequence inclusiveof an IgG1 Fc domain included herein can have 356E/358L replacing the356D/358M allotype.

In addition, many of the sequences herein have at least one thecysteines at position 220 replaced by a serine; generally this is the onthe “scFv monomer” side for most of the sequences depicted herein,although it can also be on the “Fab monomer” side, or both, to reducedisulfide formation. Specifically included within the sequences hereinare one or both of these cysteines replaced (C220S).

Thus, “isotype” as used herein is meant any of the subclasses ofimmunoglobulins defined by the chemical and antigenic characteristics oftheir constant regions. It should be understood that therapeuticantibodies can also comprise hybrids of isotypes and/or subclasses. Forexample, as shown in US Publication 2009/0163699, incorporated byreference, the present invention covers pI engineering of IgG1/G2hybrids.

The amino-terminal portion of each chain includes a variable region ofabout 100 to 110 or more amino acids primarily responsible for antigenrecognition, generally referred to in the art and herein as the “Fvdomain” or “Fv region”. In the variable region, three loops are gatheredfor each of the V domains of the heavy chain and light chain to form anantigen-binding site. Each of the loops is referred to as acomplementarity-determining region (hereinafter referred to as a “CDR”),in which the variation in the amino acid sequence is most significant.“Variable” refers to the fact that certain segments of the variableregion differ extensively in sequence among antibodies. Variabilitywithin the variable region is not evenly distributed. Instead, the Vregions consist of relatively invariant stretches called frameworkregions (FRs) of 15-30 amino acids separated by shorter regions ofextreme variability called “hypervariable regions” that are each 9-15amino acids long or longer.

Each VH and VL is composed of three hypervariable regions(“complementary determining regions,” “CDRs”) and four FRs, arrangedfrom amino-terminus to carboxy-terminus in the following order:FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4.

The hypervariable region generally encompasses amino acid residues fromabout amino acid residues 24-34 (LCDR1; “L” denotes light chain), 50-56(LCDR2) and 89-97 (LCDR3) in the light chain variable region and aroundabout 31-35B (HCDR1; “H” denotes heavy chain), 50-65 (HCDR2), and 95-102(HCDR3) in the heavy chain variable region; Kabat et al., SEQUENCES OFPROTEINS OF IMMUNOLOGICAL INTEREST, 5th Ed. Public Health Service,National Institutes of Health, Bethesda, Md. (1991) and/or thoseresidues forming a hypervariable loop (e.g. residues 26-32 (LCDR1),50-52 (LCDR2) and 91-96 (LCDR3) in the light chain variable region and26-32 (HCDR1), 53-55 (HCDR2) and 96-101 (HCDR3) in the heavy chainvariable region; Chothia and Lesk (1987) J. Mol. Biol. 196:901-917.Specific CDRs of the invention are described below.

As will be appreciated by those in the art, the exact numbering andplacement of the CDRs can be different among different numberingsystems. However, it should be understood that the disclosure of avariable heavy and/or variable light sequence includes the disclosure ofthe associated CDRs. Accordingly, the disclosure of each variable heavyregion is a disclosure of the vhCDRs (e.g. vhCDR1, vhCDR2 and vhCDR3)and the disclosure of each variable light region is a disclosure of thevhCDRs (e.g. vlCDR1, vlCDR2 and vlCDR3).

Throughout the present specification, the Kabat numbering system isgenerally used when referring to a residue in the variable domain(approximately, residues 1-107 of the light chain variable region andresidues 1-113 of the heavy chain variable region) and the EU numberingsystem for Fc regions (e.g., Kabat et al., supra (1991)).

The present invention provides a large number of different CDR sets. Inthis case, a “full CDR set” comprises the three variable light and threevariable heavy CDRs, e.g. a vlCDR1, vlCDR2, vlCDR3, vhCDR1, vhCDR2 andvhCDR3. These can be part of a larger variable light or variable heavydomain, respectfully. In addition, as more fully outlined herein, thevariable heavy and variable light domains can be on separate polypeptidechains, when a heavy and light chain is used (for example when Fabs areused), or on a single polypeptide chain in the case of scFv sequences.

The CDRs contribute to the formation of the antigen-binding, or morespecifically, epitope binding site of antibodies. “Epitope” refers to adeterminant that interacts with a specific antigen binding site in thevariable region of an antibody molecule known as a paratope. Epitopesare groupings of molecules such as amino acids or sugar side chains andusually have specific structural characteristics, as well as specificcharge characteristics. A single antigen may have more than one epitope.

The epitope may comprise amino acid residues directly involved in thebinding (also called immunodominant component of the epitope) and otheramino acid residues, which are not directly involved in the binding,such as amino acid residues which are effectively blocked by thespecifically antigen binding peptide; in other words, the amino acidresidue is within the footprint of the specifically antigen bindingpeptide.

Epitopes may be either conformational or linear. A conformationalepitope is produced by spatially juxtaposed amino acids from differentsegments of the linear polypeptide chain. A linear epitope is oneproduced by adjacent amino acid residues in a polypeptide chain.Conformational and nonconformational epitopes may be distinguished inthat the binding to the former but not the latter is lost in thepresence of denaturing solvents.

An epitope typically includes at least 3, and more usually, at least 5or 8-10 amino acids in a unique spatial conformation. Antibodies thatrecognize the same epitope can be verified in a simple immunoassayshowing the ability of one antibody to block the binding of anotherantibody to a target antigen, for example “binning.”

The carboxy-terminal portion of each chain defines a constant regionprimarily responsible for effector function. Kabat et al. collectednumerous primary sequences of the variable regions of heavy chains andlight chains. Based on the degree of conservation of the sequences, theyclassified individual primary sequences into the CDR and the frameworkand made a list thereof (see SEQUENCES OF IMMUNOLOGICAL INTEREST, 5thedition, NIH publication, No. 91-3242, E. A. Kabat et al., entirelyincorporated by reference).

In the IgG subclass of immunoglobulins, there are several immunoglobulindomains in the heavy chain. By “immunoglobulin (Ig) domain” herein ismeant a region of an immunoglobulin having a distinct tertiarystructure. Of interest in the present invention are the heavy chaindomains, including, the constant heavy (CH) domains and the hingedomains. In the context of IgG antibodies, the IgG isotypes each havethree CH regions. Accordingly, “CH” domains in the context of IgG are asfollows: “CH1” refers to positions 118-220 according to the EU index asin Kabat. “CH2” refers to positions 237-340 according to the EU index asin Kabat, and “CH3” refers to positions 341-447 according to the EUindex as in Kabat. As shown herein and described below, the pI variantscan be in one or more of the CH regions, as well as the hinge region,discussed below.

It should be noted that the sequences depicted herein start at the CH1region, position 118; the variable regions are not included except asnoted. For example, the first amino acid of SEQ ID NO: 2, whiledesignated as position“1” in the sequence listing, corresponds toposition 118 of the CH1 region, according to EU numbering.

Another type of Ig domain of the heavy chain is the hinge region. By“hinge” or “hinge region” or “antibody hinge region” or “immunoglobulinhinge region” herein is meant the flexible polypeptide comprising theamino acids between the first and second constant domains of anantibody. Structurally, the IgG CH1 domain ends at EU position 220, andthe IgG CH2 domain begins at residue EU position 237. Thus for IgG theantibody hinge is herein defined to include positions 221 (D221 in IgG1)to 236 (G236 in IgG1), wherein the numbering is according to the EUindex as in Kabat. In some embodiments, for example in the context of anFc region, the lower hinge is included, with the “lower hinge” generallyreferring to positions 226 or 230. As noted herein, pI variants can bemade in the hinge region as well.

The light chain generally comprises two domains, the variable lightdomain (containing the light chain CDRs and together with the variableheavy domains forming the Fv region), and a constant light chain region(often referred to as CL or Cκ).

Another region of interest for additional substitutions, outlined below,is the Fc region.

Thus, the present invention provides different antibody domains. Asdescribed herein and known in the art, the heterodimeric antibodies ofthe invention comprise different domains within the heavy and lightchains, which can be overlapping as well. These domains include, but arenot limited to, the Fc domain, the CH1 domain, the CH2 domain, the CH3domain, the hinge domain, the heavy constant domain (CH1-hinge-Fc domainor CH1-hinge-CH2-CH3), the variable heavy domain, the variable lightdomain, the light constant domain, FAb domains and scFv domains.

Thus, the “Fc domain” includes the —CH2-CH3 domain, and optionally ahinge domain. In the embodiments herein, when a scFv is attached to anFc domain, it is the C-terminus of the scFv construct that is attachedto the hinge of the Fc domain; for example, it is generally attached tothe sequence EPKS (SEQ ID NO:486) which is the beginning of the hinge.The heavy chain comprises a variable heavy domain and a constant domain,which includes a CH1-optional hinge-Fc domain comprising a CH2-CH3. Thelight chain comprises a variable light chain and the light constantdomain. A scFv comprises a variable heavy chain, an scFv linker, and avariable light domain. In most of the constructs and sequences outlinedherein, C-terminus of the variable light chain is attached to theN-terminus of the scFv linker, the C-terminus of which is attached tothe N-terminus of a variable heavy chain (N-vh-linker-vl-C) althoughthat can be switched (N-vl-linker-vh-C).

Some embodiments of the invention comprise at least one scFv domain,which, while not naturally occurring, generally includes a variableheavy domain and a variable light domain, linked together by a scFvlinker. As shown herein, there are a number of suitable scFv linkersthat can be used, including traditional peptide bonds, generated byrecombinant techniques.

The linker peptide may predominantly include the following amino acidresidues: Gly, Ser, Ala, or Thr. The linker peptide should have a lengththat is adequate to link two molecules in such a way that they assumethe correct conformation relative to one another so that they retain thedesired activity. In one embodiment, the linker is from about 1 to 50amino acids in length, preferably about 1 to 30 amino acids in length.In one embodiment, linkers of 1 to 20 amino acids in length may be used,with from about 5 to about 10 amino acids finding use in someembodiments. Useful linkers include glycine-serine polymers, includingfor example (GS)n, (GSGGS)n (SEQ ID NO:449), (GGGGS)n (SEQ ID NO:450),and (GGGS)n (SEQ ID NO:451), where n is an integer of at least one (andgenerally from 3 to 4), glycine-alanine polymers, alanine-serinepolymers, and other flexible linkers. Alternatively, a variety ofnonproteinaceous polymers, including but not limited to polyethyleneglycol (PEG), polypropylene glycol, polyoxyalkylenes, or copolymers ofpolyethylene glycol and polypropylene glycol, may find use as linkers,that is may find use as linkers.

Other linker sequences may include any sequence of any length of CL/CH1domain but not all residues of CL/CH1 domain; for example the first 5-12amino acid residues of the CL/CH1 domains. Linkers can be derived fromimmunoglobulin light chain, for example Cκ or Cλ. Linkers can be derivedfrom immunoglobulin heavy chains of any isotype, including for exampleCγ1, Cγ2, Cγ3, Cγ4, Cα1, Cα2, Cδ, Cε, and Cμ. Linker sequences may alsobe derived from other proteins such as Ig-like proteins (e.g. TCR, FcR,KIR), hinge region-derived sequences, and other natural sequences fromother proteins.

In some embodiments, the linker is a “domain linker”, used to link anytwo domains as outlined herein together. While any suitable linker canbe used, many embodiments utilize a glycine-serine polymer, includingfor example (GS)n, (GSGGS)n (SEQ ID NO:449), (GGGGS)n (SEQ ID NO:450),and (GGGS)n (SEQ ID NO:451), where n is an integer of at least one (andgenerally from 3 to 4 to 5) as well as any peptide sequence that allowsfor recombinant attachment of the two domains with sufficient length andflexibility to allow each domain to retain its biological function. Insome cases, and with attention being paid to “strandedness”, as outlinedbelow, charged domain linkers, as used in some embodiments of scFvlinkers can be used.

In some embodiments, the scFv linker is a charged scFv linker, a numberof which are shown in FIGS. 33A and 33B. Accordingly, the presentinvention further provides charged scFv linkers, to facilitate theseparation in pI between a first and a second monomer. That is, byincorporating a charged scFv linker, either positive or negative (orboth, in the case of scaffolds that use scFvs on different monomers),this allows the monomer comprising the charged linker to alter the pIwithout making further changes in the Fc domains. These charged linkerscan be substituted into any scFv containing standard linkers. Again, aswill be appreciated by those in the art, charged scFv linkers are usedon the correct “strand” or monomer, according to the desired changes inpI. For example, as discussed herein, to make triple F formatheterodimeric antibody, the original pI of the FAT region for each ofthe desired antigen binding domains are calculated, and one is chosen tomake an scFv, and depending on the pI, either positive or negativelinkers are chosen.

Charged domain linkers can also be used to increase the pI separation ofthe monomers of the invention as well, and thus those included in FIGS.33A and 33B can be used in any embodiment herein where a linker isutilized.

In some embodiments, the antibodies are full length. By “full lengthantibody” herein is meant the structure that constitutes the naturalbiological form of an antibody, including variable and constant regions,including one or more modifications as outlined herein, particularly inthe Fc domains to allow either heterodimerization formation or thepurification of heterodimers away from homodimers. Full lengthantibodies generally include Fab and Fc domains, and can additionallycontain extra antigen binding domains such as scFvs, as is generallydepicted in the Figures.

In one embodiment, the antibody is an antibody fragment, as long as itcontains at least one constant domain which can be engineered to produceheterodimers, such as pI engineering. Other antibody fragments that canbe used include fragments that contain one or more of the CH1, CH2, CH3,hinge and CL domains of the invention that have been pI engineered. Forexample, Fc fusions are fusions of the Fc region (CH2 and CH3,optionally with the hinge region) fused to another protein. A number ofFc fusions are known the art and can be improved by the addition of theheterodimerization variants of the invention. In the present case,antibody fusions can be made comprising CH1; CH1, CH2 and CH3; CH2; CH3;CH2 and CH3; CH1 and CH3, any or all of which can be made optionallywith the hinge region, utilizing any combination of heterodimerizationvariants described herein.

In particular, the formats depicted in FIG. 1 are antibodies, usuallyreferred to as “heterodimeric antibodies”, meaning that the protein hasat least two associated Fc sequences self-assembled into a heterodimericFc domain.

Chimeric and Humanized Antibodies

In some embodiments, the antibody can be a mixture from differentspecies, e.g. a chimeric antibody and/or a humanized antibody. Ingeneral, both “chimeric antibodies” and “humanized antibodies” refer toantibodies that combine regions from more than one species. For example,“chimeric antibodies” traditionally comprise variable region(s) from amouse (or rat, in some cases) and the constant region(s) from a human.“Humanized antibodies” generally refer to non-human antibodies that havehad the variable-domain framework regions swapped for sequences found inhuman antibodies. Generally, in a humanized antibody, the entireantibody, except the CDRs, is encoded by a polynucleotide of humanorigin or is identical to such an antibody except within its CDRs. TheCDRs, some or all of which are encoded by nucleic acids originating in anon-human organism, are grafted into the beta-sheet framework of a humanantibody variable region to create an antibody, the specificity of whichis determined by the engrafted CDRs. The creation of such antibodies isdescribed in, e.g., WO 92/11018, Jones, 1986, Nature 321:522-525,Verhoeyen et al., 1988, Science 239:1534-1536, all entirely incorporatedby reference. “Backmutation” of selected acceptor framework residues tothe corresponding donor residues is often required to regain affinitythat is lost in the initial grafted construct (U.S. Pat. Nos. 5,530,101;5,585,089; 5,693,761; 5,693,762; 6,180,370; 5,859,205; 5,821,337;6,054,297; 6,407,213, all entirely incorporated by reference). Thehumanized antibody optimally also will comprise at least a portion of animmunoglobulin constant region, typically that of a humanimmunoglobulin, and thus will typically comprise a human Fc region.Humanized antibodies can also be generated using mice with a geneticallyengineered immune system. Roque et al., 2004, Biotechnol. Prog.20:639-654, entirely incorporated by reference. A variety of techniquesand methods for humanizing and reshaping non-human antibodies are wellknown in the art (See Tsurushita & Vasquez, 2004, Humanization ofMonoclonal Antibodies, Molecular Biology of B Cells, 533-545, ElsevierScience (USA), and references cited therein, all entirely incorporatedby reference). Humanization methods include but are not limited tomethods described in Jones et al., 1986, Nature 321:522-525; Riechmannet al.,1988; Nature 332:323-329; Verhoeyen et al., 1988, Science,239:1534-1536; Queen et al., 1989, Proc Natl Acad Sci, USA 86:10029-33;He et al., 1998, J. Immunol. 160: 1029-1035; Carter et al., 1992, ProcNatl Acad Sci USA 89:4285-9, Presta et al., 1997, Cancer Res.57(20):4593-9; Gorman et al., 1991, Proc. Natl. Acad. Sci. USA88:4181-4185; O'Connor et al., 1998, Protein Eng 11:321-8, all entirelyincorporated by reference. Humanization or other methods of reducing theimmunogenicity of nonhuman antibody variable regions may includeresurfacing methods, as described for example in Roguska et al., 1994,Proc. Natl. Acad. Sci. USA 91:969-973, entirely incorporated byreference.

In certain embodiments, the antibodies of the invention comprise a heavychain variable region from a particular germline heavy chainimmunoglobulin gene and/or a light chain variable region from aparticular germline light chain immunoglobulin gene. For example, suchantibodies may comprise or consist of a human antibody comprising heavyor light chain variable regions that are “the product of” or “derivedfrom” a particular germline sequence A human antibody that is “theproduct of” or “derived from” a human germline immunoglobulin sequencecan be identified as such by comparing the amino acid sequence of thehuman antibody to the amino acid sequences of human germlineimmunoglobulins and selecting the human germline immunoglobulin sequencethat is closest in sequence (i.e., greatest % identity) to the sequenceof the human antibody. A human antibody that is “the product of” or“derived from” a particular human germline immunoglobulin sequence maycontain amino acid differences as compared to the germline sequence, dueto, for example, naturally-occurring somatic mutations or intentionalintroduction of site-directed mutation. However, a humanized antibodytypically is at least 90% identical in amino acids sequence to an aminoacid sequence encoded by a human germline immunoglobulin gene andcontains amino acid residues that identify the antibody as being derivedfrom human sequences when compared to the germline immunoglobulin aminoacid sequences of other species (e.g., murine germline sequences). Incertain cases, a humanized antibody may be at least 95, 96, 97, 98 or99%, or even at least 96%, 97%, 98%, or 99% identical in amino acidsequence to the amino acid sequence encoded by the germlineimmunoglobulin gene. Typically, a humanized antibody derived from aparticular human germline sequence will display no more than 10-20 aminoacid differences from the amino acid sequence encoded by the humangermline immunoglobulin gene (prior to the introduction of any skew, pIand ablation variants herein; that is, the number of variants isgenerally low, prior to the introduction of the variants of theinvention). In certain cases, the humanized antibody may display no morethan 5, or even no more than 4, 3, 2, or 1 amino acid difference fromthe amino acid sequence encoded by the germline immunoglobulin gene(again, prior to the introduction of any skew, pI and ablation variantsherein; that is, the number of variants is generally low, prior to theintroduction of the variants of the invention).

In one embodiment, the parent antibody has been affinity matured, as isknown in the art. Structure-based methods may be employed forhumanization and affinity maturation, for example as described in U.S.Ser. No. 11/004,590. Selection based methods may be employed to humanizeand/or affinity mature antibody variable regions, including but notlimited to methods described in Wu et al., 1999, J. Mol. Biol.294:151-162; Baca et al., 1997, J. Biol. Chem. 272(16):10678-10684;Rosok et al., 1996, J. Biol. Chem. 271(37): 22611-22618; Rader et al.,1998, Proc. Natl. Acad. Sci. USA 95: 8910-8915; Krauss et al., 2003,Protein Engineering 16(10):753-759, all entirely incorporated byreference. Other humanization methods may involve the grafting of onlyparts of the CDRs, including but not limited to methods described inU.S. Ser. No. 09/810,510; Tan et al., 2002, J. Immunol. 169:1119-1125;De Pascalis et al., 2002, J. Immunol. 169:3076-3084, all entirelyincorporated by reference.

IV. Heterodimeric Antibodies

Accordingly, in some embodiments the present invention providesheterodimeric antibodies that rely on the use of two different heavychain variant Fc sequences, that will self-assemble to formheterodimeric Fc domains and heterodimeric antibodies.

The present invention is directed to novel constructs to provideheterodimeric antibodies that allow binding to more than one antigen orligand, e.g. to allow for bispecific binding. The heterodimeric antibodyconstructs are based on the self-assembling nature of the two Fc domainsof the heavy chains of antibodies, e.g. two “monomers” that assembleinto a “dimer”. Heterodimeric antibodies are made by altering the aminoacid sequence of each monomer as more fully discussed below. Thus, thepresent invention is generally directed to the creation of heterodimericantibodies which can co-engage antigens in several ways, relying onamino acid variants in the constant regions that are different on eachchain to promote heterodimeric formation and/or allow for ease ofpurification of heterodimers over the homodimers.

Thus, the present invention provides bispecific antibodies. An ongoingproblem in antibody technologies is the desire for “bispecific”antibodies that bind to two different antigens simultaneously, ingeneral thus allowing the different antigens to be brought intoproximity and resulting in new functionalities and new therapies. Ingeneral, these antibodies are made by including genes for each heavy andlight chain into the host cells. This generally results in the formationof the desired heterodimer (A-B), as well as the two homodimers (A-A andB-B (not including the light chain heterodimeric issues)). However, amajor obstacle in the formation of bispecific antibodies is thedifficulty in purifying the heterodimeric antibodies away from thehomodimeric antibodies and/or biasing the formation of the heterodimerover the formation of the homodimers.

There are a number of mechanisms that can be used to generate theheterodimers of the present invention. In addition, as will beappreciated by those in the art, these mechanisms can be combined toensure high heterodimerization. Thus, amino acid variants that lead tothe production of heterodimers are referred to as “heterodimerizationvariants”. As discussed below, heterodimerization variants can includesteric variants (e.g. the “knobs and holes” or “skew” variants describedbelow and the “charge pairs” variants described below) as well as “pIvariants”, which allows purification of homodimers away fromheterodimers. As is generally described in WO2014/145806, herebyincorporated by reference in its entirety and specifically as below forthe discussion of “heterodimerization variants”, useful mechanisms forheterodimerization include “knobs and holes” (“KIH”; sometimes herein as“skew” variants (see discussion in WO2014/145806), “electrostaticsteering” or “charge pairs” as described in WO2014/145806, pI variantsas described in WO2014/145806, and general additional Fc variants asoutlined in WO2014/145806 and below.

In the present invention, there are several basic mechanisms that canlead to ease of purifying heterodimeric antibodies; one relies on theuse of pI variants, such that each monomer has a different pI, thusallowing the isoelectric purification of A-A, A-B and B-B dimericproteins. Alternatively, some scaffold formats, such as the “triple F”format, also allows separation on the basis of size. As is furtheroutlined below, it is also possible to “skew” the formation ofheterodimers over homodimers. Thus, a combination of stericheterodimerization variants and pI or charge pair variants findparticular use in the invention.

In general, embodiments of particular use in the present invention relyon sets of variants that include skew variants, that encourageheterodimerization formation over homodimerization formation, coupledwith pI variants, which increase the pI difference between the twomonomers.

Additionally, as more fully outlined below, depending on the format ofthe heterodimer antibody, pI variants can be either contained within theconstant and/or Fc domains of a monomer, or charged linkers, eitherdomain linkers or scFv linkers, can be used. That is, scaffolds thatutilize scFv(s) such as the Triple F format can include charged scFvlinkers (either positive or negative), that give a further pI boost forpurification purposes. As will be appreciated by those in the art, someTriple F formats are useful with just charged scFv linkers and noadditional pI adjustments, although the invention does provide pIvariants that are on one or both of the monomers, and/or charged domainlinkers as well. In addition, additional amino acid engineering foralternative functionalities may also confer pI changes, such as Fc, FcRnand KO variants.

In the present invention that utilizes pI as a separation mechanism toallow the purification of heterodimeric proteins, amino acid variantscan be introduced into one or both of the monomer polypeptides; that is,the pI of one of the monomers (referred to herein for simplicity as“monomer A”) can be engineered away from monomer B, or both monomer Aand B change be changed, with the pI of monomer A increasing and the pIof monomer B decreasing. As is outlined more fully below, the pI changesof either or both monomers can be done by removing or adding a chargedresidue (e.g. a neutral amino acid is replaced by a positively ornegatively charged amino acid residue, e.g. glycine to glutamic acid),changing a charged residue from positive or negative to the oppositecharge (aspartic acid to lysine) or changing a charged residue to aneutral residue (e.g. loss of a charge; lysine to serine.). A number ofthese variants are shown in the Figures.

Accordingly, this embodiment of the present invention provides forcreating a sufficient change in pI in at least one of the monomers suchthat heterodimers can be separated from homodimers. As will beappreciated by those in the art, and as discussed further below, thiscan be done by using a “wild type” heavy chain constant region and avariant region that has been engineered to either increase or decreaseit's pI (wt A−+B or wt A−−B), or by increasing one region and decreasingthe other region (A+−B− or A−B+).

Thus, in general, a component of some embodiments of the presentinvention are amino acid variants in the constant regions of antibodiesthat are directed to altering the isoelectric point (pI) of at leastone, if not both, of the monomers of a dimeric protein to form “pIantibodies”) by incorporating amino acid substitutions (“pI variants” or“pI substitutions”) into one or both of the monomers. As shown herein,the separation of the heterodimers from the two homodimers can beaccomplished if the pIs of the two monomers differ by as little as 0.1pH unit, with 0.2, 0.3, 0.4 and 0.5 or greater all finding use in thepresent invention.

As will be appreciated by those in the art, the number of pI variants tobe included on each or both monomer(s) to get good separation willdepend in part on the starting pI of the components, for example in thetriple F format, the starting pI of the scFv and Fab of interest. Thatis, to determine which monomer to engineer or in which “direction” (e.g.more positive or more negative), the Fv sequences of the two targetantigens are calculated and a decision is made from there. As is knownin the art, different Fvs will have different starting pIs which areexploited in the present invention. In general, as outlined herein, thepIs are engineered to result in a total pI difference of each monomer ofat least about 0.1 logs, with 0.2 to 0.5 being preferred as outlinedherein.

Furthermore, as will be appreciated by those in the art and outlinedherein, in some embodiments, heterodimers can be separated fromhomodimers on the basis of size. As shown in FIG. 1 for example, severalof the formats allow separation of heterodimers and homodimers on thebasis of size.

In the case where pI variants are used to achieve heterodimerization, byusing the constant region(s) of the heavy chain(s), a more modularapproach to designing and purifying bispecific proteins, includingantibodies, is provided. Thus, in some embodiments, heterodimerizationvariants (including skew and purification heterodimerization variants)are not included in the variable regions, such that each individualantibody must be engineered. In addition, in some embodiments, thepossibility of immunogenicity resulting from the pI variants issignificantly reduced by importing pI variants from different IgGisotypes such that pI is changed without introducing significantimmunogenicity. Thus, an additional problem to be solved is theelucidation of low pI constant domains with high human sequence content,e.g. the minimization or avoidance of non-human residues at anyparticular position.

A side benefit that can occur with this pI engineering is also theextension of serum half-life and increased FcRn binding. That is, asdescribed in U.S. Ser. No. 13/194,904 (incorporated by reference in itsentirety), lowering the pI of antibody constant domains (including thosefound in antibodies and Fc fusions) can lead to longer serum retentionin vivo. These pI variants for increased serum half life also facilitatepI changes for purification.

In addition, it should be noted that the pI variants of theheterodimerization variants give an additional benefit for the analyticsand quality control process of bispecific antibodies, as the ability toeither eliminate, minimize and distinguish when homodimers are presentis significant. Similarly, the ability to reliably test thereproducibility of the heterodimeric antibody production is important.

Heterodimerization Variants

The present invention provides heterodimeric proteins, includingheterodimeric antibodies in a variety of formats, which utilizeheterodimeric variants to allow for heterodimeric formation and/orpurification away from homodimers.

There are a number of suitable pairs of sets of heterodimerization skewvariants. These variants come in “pairs” of “sets”. That is, one set ofthe pair is incorporated into the first monomer and the other set of thepair is incorporated into the second monomer. It should be noted thatthese sets do not necessarily behave as “knobs in holes” variants, witha one-to-one correspondence between a residue on one monomer and aresidue on the other; that is, these pairs of sets form an interfacebetween the two monomers that encourages heterodimer formation anddiscourages homodimer formation, allowing the percentage of heterodimersthat spontaneously form under biological conditions to be over 90%,rather than the expected 50% (25% homodimer A/A:50% heterodimer A/B:25%homodimer B/B).

Steric Variants

In some embodiments, the formation of heterodimers can be facilitated bythe addition of steric variants. That is, by changing amino acids ineach heavy chain, different heavy chains are more likely to associate toform the heterodimeric structure than to form homodimers with the sameFc amino acid sequences. Suitable steric variants are included in FIG.29.

One mechanism is generally referred to in the art as “knobs and holes”,referring to amino acid engineering that creates steric influences tofavor heterodimeric formation and disfavor homodimeric formation canalso optionally be used; this is sometimes referred to as “knobs andholes”, as described in U.S. Ser. No. 61/596,846, Ridgway et al.,Protein Engineering 9(7):617 (1996); Atwell et al., J. Mol. Biol. 1997270:26; U.S. Pat. No. 8,216,805, all of which are hereby incorporated byreference in their entirety. The Figures identify a number of “monomerA-monomer B” pairs that rely on “knobs and holes”. In addition, asdescribed in Merchant et al., Nature Biotech. 16:677 (1998), these“knobs and hole” mutations can be combined with disulfide bonds to skewformation to heterodimerization.

An additional mechanism that finds use in the generation of heterodimersis sometimes referred to as “electrostatic steering” as described inGunasekaran et al., J. Biol. Chem. 285(25):19637 (2010), herebyincorporated by reference in its entirety. This is sometimes referred toherein as “charge pairs”. In this embodiment, electrostatics are used toskew the formation towards heterodimerization. As those in the art willappreciate, these may also have have an effect on pI, and thus onpurification, and thus could in some cases also be considered pIvariants. However, as these were generated to force heterodimerizationand were not used as purification tools, they are classified as “stericvariants”. These include, but are not limited to, D221E/P228E/L368Epaired with D221R/P228R/K409R (e.g. these are “monomer correspondingsets) and C220E/P228E/368E paired with C220R/E224R/P228R/K409R.

Additional monomer A and monomer B variants that can be combined withother variants, optionally and independently in any amount, such as pIvariants outlined herein or other steric variants that are shown in FIG.37 of US 2012/0149876, the figure and legend and SEQ ID NOs of which areincorporated expressly by reference herein.

In some embodiments, the steric variants outlined herein can beoptionally and independently incorporated with any pI variant (or othervariants such as Fc variants, FcRn variants, etc.) into one or bothmonomers, and can be independently and optionally included or excludedfrom the proteins of the invention.

A list of suitable skew variants is found in FIG. 29, with FIG. 34showing some pairs of particular utility in many embodiments. Ofparticular use in many embodiments are the pairs of sets including, butnot limited to, S364K/E357Q: L368D/K370S; L368D/K370S: S364K;L368E/K370S: S364K; T411T/E360E/Q362E: D401K; L368D/K370S: S364K/E357Land K370S: S364K/E357Q. In terms of nomenclature, the pair “S364K/E357Q:L368D/K370S” means that one of the monomers has the double variant setS364K/E357Q and the other has the double variant set L368D/K370S.

pI (Isoelectric point) Variants for Heterodimers

In general, as will be appreciated by those in the art, there are twogeneral categories of pI variants: those that increase the pI of theprotein (basic changes) and those that decrease the pI of the protein(acidic changes). As described herein, all combinations of thesevariants can be done: one monomer may be wild type, or a variant thatdoes not display a significantly different pI from wild-type, and theother can be either more basic or more acidic. Alternatively, eachmonomer is changed, one to more basic and one to more acidic.

Preferred combinations of pI variants are shown in FIG. 30. As outlinedherein and shown in the figures, these changes are shown relative toIgG1, but all isotypes can be altered this way, as well as isotypehybrids. In the case where the heavy chain constant domain is fromIgG2-4, R133E and R133Q can also be used.

In one embodiment, for example in the bottle opener format, a preferredcombination of pI variants has one monomer (the negative Fab side)comprising 208D/295E/384D/418E/421D variants(N208D/Q295E/N384D/Q418E/N421D when relative to human IgG1) and a secondmonomer (the positive scFv side) comprising a positively charged scFvlinker, including (GKPGS)₄ (SEQ ID NO:487). However, as will beappreciated by those in the art, the first monomer includes a CH1domain, including position 208. Accordingly, in constructs that do notinclude a CH1 domain (for example for heterodimeric Fc fusion proteinsthat do not utilize a CH1 domain on one of the domains, for example in adual scFv format), a preferred negative pI variant Fc set includes295E/384D/418E/421D variants (Q295E/N384D/Q418E/N421D when relative tohuman IgG1).

Antibody Heterodimers Light Chain Variants

In the case of antibody based heterodimers, e.g. where at least one ofthe monomers comprises a light chain in addition to the heavy chaindomain, pI variants can also be made in the light chain. Amino acidsubstitutions for lowering the pI of the light chain include, but arenot limited to, K126E, K126Q, K145E, K145Q, N152D, S156E, K169E, S202E,K207E and adding peptide DEDE at the c-terminus of the light chain.Changes in this category based on the constant lambda light chaininclude one or more substitutions at R108Q, Q124E, K126Q, N138D, K145Tand Q199E. In addition, increasing the pI of the light chains can alsobe done.

Isotypic Variants

In addition, many embodiments of the invention rely on the “importation”of pI amino acids at particular positions from one IgG isotype intoanother, thus reducing or eliminating the possibility of unwantedimmunogenicity being introduced into the variants. A number of these areshown in FIG. 21 of US Publ. 2014/0370013, hereby incorporated byreference. That is, IgG1 is a common isotype for therapeutic antibodiesfor a variety of reasons, including high effector function. However, theheavy constant region of IgG1 has a higher pI than that of IgG2 (8.10versus 7.31). By introducing IgG2 residues at particular positions intothe IgG1 backbone, the pI of the resulting monomer is lowered (orincreased) and additionally exhibits longer serum half-life. Forexample, IgG1 has a glycine (pI 5.97) at position 137, and IgG2 has aglutamic acid (pI 3.22); importing the glutamic acid will affect the pIof the resulting protein. As is described below, a number of amino acidsubstitutions are generally required to significant affect the pI of thevariant antibody. However, it should be noted as discussed below thateven changes in IgG2 molecules allow for increased serum half-life.

In other embodiments, non-isotypic amino acid changes are made, eitherto reduce the overall charge state of the resulting protein (e.g. bychanging a higher pI amino acid to a lower pI amino acid), or to allowaccommodations in structure for stability, etc. as is more furtherdescribed below.

In addition, by pI engineering both the heavy and light constantdomains, significant changes in each monomer of the heterodimer can beseen. As discussed herein, having the pIs of the two monomers differ byat least 0.5 can allow separation by ion exchange chromatography orisoelectric focusing, or other methods sensitive to isoelectric point.

Calculating pI

The pI of each monomer can depend on the pI of the variant heavy chainconstant domain and the pI of the total monomer, including the variantheavy chain constant domain and the fusion partner. Thus, in someembodiments, the change in pI is calculated on the basis of the variantheavy chain constant domain, using the chart in the FIG. 19 of US Pub.2014/0370013. As discussed herein, which monomer to engineer isgenerally decided by the inherent pI of the Fv and scaffold regions.Alternatively, the pI of each monomer can be compared.

pI Variants that Also Confer Better FcRn In Vivo Binding

In the case where the pI variant decreases the pI of the monomer, theycan have the added benefit of improving serum retention in vivo.

Although still under examination, Fc regions are believed to have longerhalf-lives in vivo, because binding to FcRn at pH 6 in an endosomesequesters the Fc (Ghetie and Ward, 1997 Immunol Today. 18(12): 592-598,entirely incorporated by reference). The endosomal compartment thenrecycles the Fc to the cell surface. Once the compartment opens to theextracellular space, the higher pH, ˜7.4, induces the release of Fc backinto the blood. In mice, Dall'Acqua et al. showed that Fc mutants withincreased FcRn binding at pH 6 and pH 7.4 actually had reduced serumconcentrations and the same half life as wild-type Fc (Dall'Acqua et al.2002, J. Immunol. 169:5171-5180, entirely incorporated by reference).The increased affinity of Fc for FcRn at pH 7.4 is thought to forbid therelease of the Fc back into the blood. Therefore, the Fc mutations thatwill increase Fc's half-life in vivo will ideally increase FcRn bindingat the lower pH while still allowing release of Fc at higher pH. Theamino acid histidine changes its charge state in the pH range of 6.0 to7.4. Therefore, it is not surprising to find His residues at importantpositions in the Fc/FcRn complex.

Recently it has been suggested that antibodies with variable regionsthat have lower isoelectric points may also have longer serum half-lives(Igawa et al., 2010 PEDS. 23(5): 385-392, entirely incorporated byreference). However, the mechanism of this is still poorly understood.Moreover, variable regions differ from antibody to antibody. Constantregion variants with reduced pI and extended half-life would provide amore modular approach to improving the pharmacokinetic properties ofantibodies, as described herein.

Additional Fc Variants for Additional Functionality

In addition to pI amino acid variants, there are a number of useful Fcamino acid modification that can be made for a variety of reasons,including, but not limited to, altering binding to one or more FcγRreceptors, altered binding to FcRn receptors, etc.

Accordingly, the proteins of the invention can include amino acidmodifications, including the heterodimerization variants outlinedherein, which includes the pI variants and steric variants. Each set ofvariants can be independently and optionally included or excluded fromany particular heterodimeric protein.

FcγR Variants

Accordingly, there are a number of useful Fc substitutions that can bemade to alter binding to one or more of the FcγR receptors.Substitutions that result in increased binding as well as decreasedbinding can be useful. For example, it is known that increased bindingto Fc□RIIIa generally results in increased ADCC (antibody dependentcell-mediated cytotoxicity; the cell-mediated reaction whereinnonspecific cytotoxic cells that express FcγRs recognize bound antibodyon a target cell and subsequently cause lysis of the target cell).Similarly, decreased binding to FcγRIIb (an inhibitory receptor) can bebeneficial as well in some circumstances. Amino acid substitutions thatfind use in the present invention include those listed in U.S. Ser. No.11/124,620 (particularly FIG. 41), Ser. Nos. 11/174,287, 11/396,495,11/538,406, all of which are expressly incorporated herein by referencein their entirety and specifically for the variants disclosed therein.Particular variants that find use include, but are not limited to, 236A,239D, 239E, 332E, 332D, 239D/332E, 267D, 267E, 328F, 267E/328F,236A/332E, 239D/332E/330Y, 239D, 332E/330L, 243A, 243L, 264A, 264V and299T.

In addition, there are additional Fc substitutions that find use inincreased binding to the FcRn receptor and increased serum half life, asspecifically disclosed in U.S. Ser. No. 12/341,769, hereby incorporatedby reference in its entirety, including, but not limited to, 434S, 434A,428L, 308F, 259I, 428L/434S, 259I/308F, 436I/428L, 436I or V/434S,436V/428L and 259I/308F/428L.

Ablation Variants

Similarly, another category of functional variants are “FcγR ablationvariants” or “Fc knock out (FcKO or KO)” variants. In these embodiments,for some therapeutic applications, it is desirable to reduce or removethe normal binding of the Fc domain to one or more or all of the Fcγreceptors (e.g. FcγR1, FcγRIIa, FcγRIIb, FcγRIIIa, etc.) to avoidadditional mechanisms of action. That is, for example, in manyembodiments, particularly in the use of bispecific antibodies that bindCD3 monovalently it is generally desirable to ablate FcγRIIIa binding toeliminate or significantly reduce ADCC activity. wherein one of the Fcdomains comprises one or more Fcγ receptor ablation variants. Theseablation variants are depicted in FIG. 31, and each can be independentlyand optionally included or excluded, with preferred aspects utilizingablation variants selected from the group consisting of G236R/L328R,E233P/L234V/L235A/G236del/S239K, E233P/L234V/L235A/G236del/S267K,E233P/L234V/L235A/G236del/S239K/A327G,E233P/L234V/L235A/G236del/S267K/A327G and E233P/L234V/L235A/G236del. Itshould be noted that the ablation variants referenced herein ablate FcγRbinding but generally not FcRn binding.

Combination of Heterodimeric and Fc Variants

As will be appreciated by those in the art, all of the recitedheterodimerization variants (including skew and/or pI variants) can beoptionally and independently combined in any way, as long as they retaintheir “strandedness” or “monomer partition”. In addition, all of thesevariants can be combined into any of the heterodimerization formats.

In the case of pI variants, while embodiments finding particular use areshown in the Figures, other combinations can be generated, following thebasic rule of altering the pI difference between two monomers tofacilitate purification.

In addition, any of the heterodimerization variants, skew and pI, arealso independently and optionally combined with Fc ablation variants, Fcvariants, FcRn variants, as generally outlined herein.

Useful Formats of the Invention

As will be appreciated by those in the art and discussed more fullybelow, the heterodimeric fusion proteins of the present invention cantake on a wide variety of configurations, as are generally depicted inFIG. 1. Some figures depict “single ended” configurations, where thereis one type of specificity on one “arm” of the molecule and a differentspecificity on the other “arm”. Other figures depict “dual ended”configurations, where there is at least one type of specificity at the“top” of the molecule and one or more different specificities at the“bottom” of the molecule. Thus, the present invention is directed tonovel immunoglobulin compositions that co-engage a different first and asecond antigen.

As will be appreciated by those in the art, the heterodimeric formats ofthe invention can have different valencies as well as be bispecific.That is, heterodimeric antibodies of the invention can be bivalent andbispecific, wherein one target tumor antigen (e.g. CD3) is bound by onebinding domain and the other target tumor antigen (e.g. CD20, CD38,CD123, etc.) is bound by a second binding domain. The heterodimericantibodies can also be trivalent and bispecific, wherein the firstantigen is bound by two binding domains and the second antigen by asecond binding domain. As is outlined herein, when CD3 is one of thetarget antigens, it is preferable that the CD3 is bound onlymonovalently, to reduce potential side effects.

The present invention utilizes anti-CD3 antigen binding domains incombination with anti-target tumor antigen (TTA) antigen bindingdomains. As will be appreciated by those in the art, any collection ofanti-CD3 CDRs, anti-CD3 variable light and variable heavy domains, Fabsand scFvs as depicted in any of the Figures (see particularly FIGS. 2through 7, and FIGS. 68A-68Z) can be used. Similarly, any of theanti-TTA antigen binding domains can be used, e.g. anti-CD38, anti-CD20,anti-CD19 and anti-CD123 antigen binding domains, whether CDRs, variablelight and variable heavy domains, Fabs and scFvs as depicted in any ofthe Figures can be used, optionally and independently combined in anycombination.

Bottle Opener Format

One heterodimeric scaffold that finds particular use in the presentinvention is the “triple F” or “bottle opener” scaffold format as shownin FIGS. 1A, A and B. In this embodiment, one heavy chain of theantibody contains an single chain Fv (“scFv”, as defined below) and theother heavy chain is a “regular” FAb format, comprising a variable heavychain and a light chain. This structure is sometimes referred to hereinas “triple F” format (scFv-FAb-Fc) or the “bottle-opener” format, due toa rough visual similarity to a bottle-opener (see FIG. 1). The twochains are brought together by the use of amino acid variants in theconstant regions (e.g. the Fc domain, the CH1 domain and/or the hingeregion) that promote the formation of heterodimeric antibodies as isdescribed more fully below.

There are several distinct advantages to the present “triple F” format.As is known in the art, antibody analogs relying on two scFv constructsoften have stability and aggregation problems, which can be alleviatedin the present invention by the addition of a “regular” heavy and lightchain pairing. In addition, as opposed to formats that rely on two heavychains and two light chains, there is no issue with the incorrectpairing of heavy and light chains (e.g. heavy 1 pairing with light 2,etc.).

Many of the embodiments outlined herein rely in general on the bottleopener format that comprises a first monomer comprising an scFv,comprising a variable heavy and a variable light domain, covalentlyattached using an scFv linker (charged, in many but not all instances),where the scFv is covalently attached to the N-terminus of a first Fcdomain usually through a domain linker (which, as outlined herein caneither be un-charged or charged). The second monomer of the bottleopener format is a heavy chain, and the composition further comprises alight chain.

In general, in many preferred embodiments, the scFv is the domain thatbinds to the CD3, with the Fab of the heavy and light chains binding tothe other TTA.

In addition, the Fc domains of the invention generally comprise skewvariants (e.g. a set of amino acid substitutions as shown in FIG. 29 andFIG. 34, with particularly useful skew variants being selected from thegroup consisting of S364K/E357Q: L368D/K370S; L368D/K370S: S364K;L368E/K370S: S364K; T411T/E360E/Q362E: D401K; L368D/K370S: S364K/E357Land K370S: S364K/E357Q), optionally ablation variants (including thoseshown in FIG. 31), optionally charged scFv linkers (including thoseshown in FIGS. 33A and 33B) and the heavy chain comprises pI variants(including those shown in FIG. 30).

In some embodiments, any of the vh and vl sequences depicted herein(including all vh and vl sequences depicted in the Figures, includingthose directed to CD20, CD38 and CD123) can be added to the bottleopener backbone formats of FIG. 162 as the “Fab side”, using any of theanti-CD3 scFv sequences shown in the Figures. Anti-CD3 sequences findingparticular use in these embodiments are anti-CD3 H1.30 L1.47, anti-CD3H1.32 L1.47, anti-CD3 H1.89 L1.47, anti-CD3 H1.90 L1.47, anti-CD3 H1.33L1.47 and anti-CD3 H1.31 L1.47, attached as the scFv side of thebackbones shown in FIG. 162.

The present invention provides bottle opener formats where the anti-CD3scFv sequences are as shown in FIG. 2 to FIG. 7 and FIGS. 68A-68Z,including any combination with the backbone formats of FIG. 162. Inaddition, any of the anti-CD3 vh and vl sequence as shown in FIG. 2 toFIG. 7 and FIGS. 68A-68Z can be used as the Fab side.

The present invention provides bottle opener formats with CD38 antigenbinding domains wherein the anti-CD38 sequences are as shown in theFigures, including FIGS. 8 to 10. As above, each vh and vl anti-CD38sequence can be either the Fab side or the scFv side, and can be linkedas one of the antigen binding domains of a bottle opener format,including those of FIG. 162. When the anti-CD38 sequences are the Fabside, any anti-CD3 scFv sequences of the Figures can be used,particularly including anti-CD3 H1.30_L1.47, anti-CD3 H1.32_L1.47,anti-CD3 H1.89_L1.47, anti-CD3 H1.90_L1.47, anti-CD3 H1.33_L1.47 andanti-CD3 H1.31_L1.47, attached as the scFv side of the backbones shownin FIG. 162.

The present invention provides bottle opener formats with CD20 antigenbinding domains wherein the anti-CD20 sequences are as shown in theFigures. As above, each vh and vl anti-CD20 sequence can be either theFab side or the scFv side, and can be linked as one of the antigenbinding domains of a bottle opener format, including those of FIG. 162.When the anti-CD20 sequences are the Fab side, any anti-CD3 scFvsequences of the Figures can be used, particularly including anti-CD3H1.30_L1.47, anti-CD3 H1.32_L1.47, anti-CD3 H1.89_L1.47, anti-CD3H1.90_L1.47, anti-CD3 H1.33_L1.47 and anti-CD3 H1.31_L1.47, attached asthe scFv side of the backbones shown in FIG. 162.

The present invention provides bottle opener formats with CD123 antigenbinding domains wherein the anti-CD123 sequences are as shown in theFigures. As above, each vh and vl anti-CD123 sequence can be either theFab side or the scFv side, and can be linked as one of the antigenbinding domains of a bottle opener format, including those of FIG. 162.When the anti-CD123 sequences are the Fab side, any anti-CD3 scFvsequences of the Figures can be used, particularly including anti-CD3H1.30 L1.47, anti-CD3 H1.32_L1.47, anti-CD3 H1.89_L1.47, anti-CD3H1.90_L1.47, anti-CD3 H1.33_L1.47 and anti-CD3 H1.31_L1.47, attached asthe scFv side of the backbones shown in FIG. 162.

mAb-Fv Format

One heterodimeric scaffold that finds particular use in the presentinvention is the mAb-Fv format shown in FIG. 1. In this embodiment, theformat relies on the use of a C-terminal attachment of an “extra”variable heavy domain to one monomer and the C-terminal attachment of an“extra” variable light domain to the other monomer, thus forming a thirdantigen binding domain, wherein the Fab portions of the two monomersbind a TTA and the “extra” scFv domain binds CD3.

In this embodiment, the first monomer comprises a first heavy chain,comprising a first variable heavy domain and a first constant heavydomain comprising a first Fc domain, with a first variable light domaincovalently attached to the C-terminus of the first Fc domain using adomain linker (vh1-CH1-hinge-CH2-CH3-[optional linker]-vl2). The secondmonomer comprises a second variable heavy domain of the second constantheavy domain comprising a second Fc domain, and a third variable heavydomain covalently attached to the C-terminus of the second Fc domainusing a domain linker (vj1-CH1-hinge-CH2-CH3-[optional linker]-vh2. Thetwo C-terminally attached variable domains make up a scFv that binds CD3(as it is less preferred to have bivalent CD3 binding). This embodimentfurther utilizes a common light chain comprising a variable light domainand a constant light domain, that associates with the heavy chains toform two identical Fabs that bind a TTA. As for many of the embodimentsherein, these constructs include skew variants, pI variants, ablationvariants, additional Fc variants, etc. as desired and described herein.

The present invention provides mAb-Fv formats where the anti-CD3 scFvsequences are as shown in FIG. 2 to FIG. 7 and FIGS. 68A-68Z.

The present invention provides mAb-Fv formats wherein the anti-CD38sequences are as shown in FIGS. 8 to 10.

The present invention provides mAb-Fv formats with CD20 antigen bindingdomains wherein the anti-CD20 sequences are as shown in the Figures.

The present invention provides mAb-Fv formats with CD19 antigen bindingdomains wherein the anti-CD19 sequences are as shown in the Figures.

The present invention provides mAb-Fv formats with CD123 antigen bindingdomains wherein the anti-CD123 sequences are as shown in the Figures.

The present invention provides mAb-Fv formats comprising ablationvariants as shown in FIG. 31.

The present invention provides mAb-Fv formats comprising skew variantsas shown in FIGS. 29 and 34.

mAb-scFv

One heterodimeric scaffold that finds particular use in the presentinvention is the mAb-scFv format shown in FIG. 1. In this embodiment,the format relies on the use of a C-terminal attachment of a scFv to oneof the monomers, thus forming a third antigen binding domain, whereinthe Fab portions of the two monomers bind a TTA and the “extra” scFvdomain binds CD3. Thus, the first monomer comprises a first heavy chain(comprising a variable heavy domain and a constant domain), with aC-terminally covalently attached scFv comprising a scFv variable lightdomain, an scFv linker and a scFv variable heavy domain in eitherorientation (vh1-CH1-hinge-CH2-CH3-[optional linker]-vh2-scFv linker-vl2or vh1-CH1-hinge-CH2-CH3-[optional linker]-vl2-scFv linker-vh2). Thisembodiment further utilizes a common light chain comprising a variablelight domain and a constant light domain, that associates with the heavychains to form two identical Fabs that bind a TTA. As for many of theembodiments herein, these constructs include skew variants, pI variants,ablation variants, additional Fc variants, etc. as desired and describedherein.

The present invention provides mAb-Fv formats where the anti-CD3 scFvsequences are as shown in FIG. 2 to FIG. 7 and FIGS. 68A-68Z.

The present invention provides mAb-Fv formats wherein the anti-CD38sequences are as shown in FIGS. 8 to 10.

The present invention provides mAb-Fv formats with CD20 antigen bindingdomains wherein the anti-CD20 sequences are as shown in the Figures.

The present invention provides mAb-Fv formats with CD19 antigen bindingdomains wherein the anti-CD19 sequences are as shown in the Figures.

The present invention provides mAb-Fv formats with CD123 antigen bindingdomains wherein the anti-CD123 sequences are as shown in the Figures.

The present invention provides mAb-Fv formats comprising ablationvariants as shown in FIG. 31.

The present invention provides mAb-Fv formats comprising skew variantsas shown in FIGS. 29 and 34.

Central scFv

One heterodimeric scaffold that finds particular use in the presentinvention is the Central-scFv format shown in FIG. 1. In thisembodiment, the format relies on the use of an inserted scFv domain thusforming a third antigen binding domain, wherein the Fab portions of thetwo monomers bind a TTA and the “extra” scFv domain binds CD3. The scFvdomain is inserted between the Fc domain and the CH1-Fv region of one ofthe monomers, thus providing a third antigen binding domain.

In this embodiment, one monomer comprises a first heavy chain comprisinga first variable heavy domain, a CH1 domain (and optional hinge) and Fcdomain, with a scFv comprising a scFv variable light domain, an scFvlinker and a scFv variable heavy domain. The scFv is covalently attachedbetween the C-terminus of the CH1 domain of the heavy constant domainand the N-terminus of the first Fc domain using optional domain linkers(vh1-CH1-[optional linker]-vh2-scFv linker-vl2-[optional linkerincluding the hinge]-CH2-CH3, or the opposite orientation for the scFv,vh1-CH1-[optional linker]-vl2-scFv linker-vh2-[optional linker includingthe hinge]-CH2-CH3). The other monomer is a standard Fab side. Thisembodiment further utilizes a common light chain comprising a variablelight domain and a constant light domain, that associates with the heavychains to form two identical Fabs that bind a TTA. As for many of theembodiments herein, these constructs include skew variants, pI variants,ablation variants, additional Fc variants, etc. as desired and describedherein.

The present invention provides Central-scFv formats where the anti-CD3scFv sequences are as shown in FIG. 2 to FIG. 7 and FIGS. 68A-68Z.

The present invention provides Central-scFv formats wherein theanti-CD38 sequences are as shown in FIGS. 8 to 10.

The present invention provides Central-scFv formats with CD20 antigenbinding domains wherein the anti-CD20 sequences are as shown in theFigures.

The present invention provides Central-scFv formats with CD19 antigenbinding domains wherein the anti-CD19 sequences are as shown in theFigures.

The present invention provides Central-scFv formats with CD123 antigenbinding domains wherein the anti-CD123 sequences are as shown in v

The present invention provides Central-scFv formats comprising ablationvariants as shown in FIG. 31.

The present invention provides Central-scFv formats comprising skewvariants as shown in FIGS. 29 and 34.

Central-Fv Format

One heterodimeric scaffold that finds particular use in the presentinvention is the Central-Fv format shown in FIG. 1. In this embodiment,the format relies on the use of an inserted scFv domain thus forming athird antigen binding domain, wherein the Fab portions of the twomonomers bind a TTA and the “extra” scFv domain binds CD3. The scFvdomain is inserted between the Fc domain and the CH1-Fv region of themonomers, thus providing a third antigen binding domain, wherein eachmonomer contains a component of the scFv (e.g. one monomer comprises avariable heavy domain and the other a variable light domain).

In this embodiment, one monomer comprises a first heavy chain comprisinga first variable heavy domain, a CH1 domain, and Fc domain and anadditional variable light domain. The light domain is covalentlyattached between the C-terminus of the CH1 domain of the heavy constantdomain and the N-terminus of the first Fc domain using domain linkers(vh1-CH1-[optional linker]-vl2-hinge-CH2-CH3). The other monomercomprises a first heavy chain comprising a first variable heavy domain,a CH1 domain and Fc domain and an additional variable heavy domain(vh1-CH1-[optional linker]-vh2-hinge-CH2-CH3). The light domain iscovalently attached between the C-terminus of the CH1 domain of theheavy constant domain and the N-terminus of the first Fc domain usingdomain linkers.

This embodiment further utilizes a common light chain comprising avariable light domain and a constant light domain, that associates withthe heavy chains to form two identical Fabs that bind a TTA. As for manyof the embodiments herein, these constructs include skew variants, pIvariants, ablation variants, additional Fc variants, etc. as desired anddescribed herein.

The present invention provides Central-Fv formats where the anti-CD3scFv sequences are as shown in FIG. 2 to FIG. 7 and FIGS. 68A-68Z.

The present invention provides Central-Fv formats wherein the anti-CD38sequences are as shown in FIGS. 8 to 10.

The present invention provides Central-Fv formats with CD20 antigenbinding domains wherein the anti-CD20 sequences are as shown in theFigures.

The present invention provides Central-Fv formats with CD19 antigenbinding domains wherein the anti-CD19 sequences are as shown in theFigures.

The present invention provides Central-Fv formats with CD123 antigenbinding domains wherein the anti-CD123 sequences are as shown in theFigures.

The present invention provides Central-Fv formats comprising ablationvariants as shown in FIG. 31.

The present invention provides Central-Fv formats comprising skewvariants as shown in FIGS. 29 and 34.

One Armed Central-scFv

One heterodimeric scaffold that finds particular use in the presentinvention is the one armed central-scFv format shown in FIG. 1. In thisembodiment, one monomer comprises just an Fc domain, while the othermonomer uses an inserted scFv domain thus forming the second antigenbinding domain. In this format, either the Fab portion binds a TTA andthe scFv binds CD3 or vice versa. The scFv domain is inserted betweenthe Fc domain and the CH1-Fv region of one of the monomers.

In this embodiment, one monomer comprises a first heavy chain comprisinga first variable heavy domain, a CH1 domain and Fc domain, with a scFvcomprising a scFv variable light domain, an scFv linker and a scFvvariable heavy domain. The scFv is covalently attached between theC-terminus of the CH1 domain of the heavy constant domain and theN-terminus of the first Fc domain using domain linkers. The secondmonomer comprises an Fc domain. This embodiment further utilizes a lightchain comprising a variable light domain and a constant light domain,that associates with the heavy chain to form a Fab. As for many of theembodiments herein, these constructs include skew variants, pI variants,ablation variants, additional Fc variants, etc. as desired and describedherein.

The present invention provides one armed central-scFv formats where theanti-CD3 scFv sequences are as shown in FIG. 2 to FIG. 7 and FIGS.68A-68Z.

The present invention provides one armed central-scFv formats whereinthe anti-CD38 sequences are as shown in FIGS. 8 to 10.

The present invention provides one armed central-scFv formats with CD20antigen binding domains wherein the anti-CD20 sequences are as shown inthe Figures.

The present invention provides one armed central-scFv formats with CD19antigen binding domains wherein the anti-CD19 sequences are as shown inthe Figures.

The present invention provides one armed central-scFv formats with CD123antigen binding domains wherein the anti-CD123 sequences are as shown inthe Figures.

The present invention provides one armed central-scFv formats comprisingablation variants as shown in FIG. 31.

The present invention provides one armed central-scFv formats comprisingskew variants as shown in FIGS. 29 and 34.

Dual scFv Formats

The present invention also provides dual scFv formats as are known inthe art and shown in FIG. 1.

The present invention provides dual scFv formats where the anti-CD3 scFvsequences are as shown in FIG. 2 to FIG. 7 and FIGS. 68A-68Z.

The present invention provides dual scFv formats wherein the anti-CD38sequences are as shown in FIGS. 8 to 10.

The present invention provides dual scFv formats with CD20 antigenbinding domains wherein the anti-CD20 sequences are as shown in theFigures.

The present invention provides dual scFv formats with CD19 antigenbinding domains wherein the anti-CD19 sequences are as shown in theFigures.

The present invention provides dual scFv formats with CD123 antigenbinding domains wherein the anti-CD123 sequences are as shown in theFigures.

The present invention provides dual scFv formats comprising ablationvariants as shown in FIG. 31.

The present invention provides dual scFv formats comprising skewvariants as shown in FIGS. 29 and 34.

The present invention provides dual scFv formats comprising pI variantsand/or charged scFv linkers (in general, either one monomer comprisesQ295E/N384D/Q418E/N481D and the other a positively charged scFv linker,or they both comprise oppositely charged scFv linkers).

Target Antigens

The bispecific antibodies of the invention have two different antigenbinding domains: one that binds to CD3 (generally monovalently), and onethat binds to a target tumor antigen (sometimes referred to herein as“TTA”). Suitable target tumor antigens include, but are not limited to,CD20, CD38, CD123; ROR1, ROR2, BCMA; PSMA; SSTR2; SSTR5, CD19, FLT3,CD33, PSCA, ADAM 17, CEA, Her2, EGFR, EGFR-vIII, CD30, FOLR1, GD-2,CA-IX, Trop-2, CD70, CD38, mesothelin, EphA2, CD22, CD79b, GPNMB, CD56,CD138, CD52, CD74, CD30, CD123, RON, ERBB2, and EGFR.

The “triple F” format is particularly beneficial for targeting two (ormore) distinct antigens. (As outlined herein, this targeting can be anycombination of monovalent and divalent binding, depending on theformat). Thus the immunoglobulins herein preferably co-engage two targetantigens. Each monomer's specificity can be selected from the listsherein. Additional useful bispecific formats for use with an anti-CD3binding domain are shown in FIG. 1.

Particular suitable applications of the heterodimeric antibodies hereinare co-target pairs for which it is beneficial or critical to engageeach target antigen monovalently. Such antigens may be, for example,immune receptors that are activated upon immune complexation. Cellularactivation of many immune receptors occurs only by cross-linking,achieved typically by antibody/antigen immune complexes, or via effectorcell to target cell engagement. For some immune receptors, for examplethe CD3 signaling receptor on T cells, activation only upon engagementwith co-engaged target is critical, as nonspecific cross-linking in aclinical setting can elicit a cytokine storm and toxicity.Therapeutically, by engaging such antigens monovalently rather thanmultivalently, using the immunoglobulins herein, such activation occursonly in response to cross-linking only in the microenvironment of theprimary target antigen. The ability to target two different antigenswith different valencies is a novel and useful aspect of the presentinvention. Examples of target antigens for which it may betherapeutically beneficial or necessary to co-engage monovalentlyinclude but are not limited to immune activating receptors such as CD3,FcγRs, toll-like receptors (TLRs) such as TLR4 and TLR9, cytokine,chemokine, cytokine receptors, and chemokine receptors. In manyembodiments, one of the antigen binding sites binds to CD3, and in someembodiments it is the scFv-containing monomer.

Virtually any antigen may be targeted by the immunoglobulins herein,including but not limited to proteins, subunits, domains, motifs, and/orepitopes belonging to the following list of target antigens, whichincludes both soluble factors such as cytokines and membrane-boundfactors, including transmembrane receptors: 17-IA, 4-1BB, 4Dc,6-keto-PGF1a, 8-iso-PGF2a, 8-oxo-dG, A1 Adenosine Receptor, A33, ACE,ACE-2, Activin, Activin A, Activin AB, Activin B, Activin C, ActivinRIA, Activin RIA ALK-2, Activin RIB ALK-4, Activin RIIA, Activin RIIB,ADAM, ADAM10, ADAM12, ADAM15, ADAM17/TACE, ADAMS, ADAMS, ADAMTS,ADAMTS4, ADAMTS5, Addressins, aFGF, ALCAM, ALK, ALK-1, ALK-7,alpha-1-antitrypsin, alpha-V/beta-1 antagonist, ANG, Ang, APAF-1, APE,APJ, APP, APRIL, AR, ARC, ART, Artemin, anti-Id, ASPARTIC, Atrialnatriuretic factor, av/b3 integrin, Axl, b2M, B7-1, B7-2, B7-H,B-lymphocyte Stimulator (BlyS), BACE, BACE-1, Bad, BAFF, BAFF-R, Bag-1,BAK, Bax, BCA-1, BCAM, Bcl, BCMA, BDNF, b-ECGF, bFGF, BID, Bik, BIM,BLC, BL-CAM, BLK, BMP, BMP-2 BMP-2a, BMP-3 Osteogenin, BMP-4 BMP-2b,BMP-5, BMP-6 Vgr-1, BMP-7 (OP-1), BMP-8 (BMP-8a, OP-2), BMPR, BMPR-IA(ALK-3), BMPR-IB (ALK-6), BRK-2, RPK-1, BMPR-II (BRK-3), BMPs, b-NGF,BOK, Bombesin, Bone-derived neurotrophic factor, BPDE, BPDE-DNA, BTC,complement factor 3 (C3), C3a, C4, C5, C5a, C10, CA125, CAD-8,Calcitonin, cAMP, carcinoembryonic antigen (CEA), carcinoma-associatedantigen, Cathepsin A, Cathepsin B, Cathepsin C/DPPI, Cathepsin D,Cathepsin E, Cathepsin H, Cathepsin L, Cathepsin O, Cathepsin S,Cathepsin V, Cathepsin X/Z/P, CBL, CCI, CCK2, CCL, CCL1, CCL11, CCL12,CCL13, CCL14, CCL15, CCL16, CCL17, CCL18, CCL19, CCL2, CCL20, CCL21,CCL22, CCL23, CCL24, CCL25, CCL26, CCL27, CCL28, CCL3, CCL4, CCL5, CCL6,CCL7, CCL8, CCL9/10, CCR, CCR1, CCR10, CCR10, CCR2, CCR3, CCR4, CCR5,CCR6, CCR7, CCR8, CCR9, CD1, CD2, CD3, CD3E, CD4, CD5, CD6, CD7, CD8,CD10, CD11a, CD11b, CD11c, CD13, CD14, CD15, CD16, CD18, CD19, CD20,CD21, CD22, CD23, CD25, CD27L, CD28, CD29, CD30, CD30L, CD32, CD33 (p67proteins), CD34, CD38, CD40, CD40L, CD44, CD45, CD46, CD49a, CD52, CD54,CD55, CD56, CD61, CD64, CD66e, CD74, CD80 (B7-1), CD89, CD95, CD123,CD137, CD138, CD140a, CD146, CD147, CD148, CD152, CD164, CEACAM5, CFTR,cGMP, CINC, Clostridium botulinum toxin, Clostridium perfringens toxin,CKb8-1, CLC, CMV, CMV UL, CNTF, CNTN-1, COX, C-Ret, CRG-2, CT-1, CTACK,CTGF, CTLA-4, CX3CL1, CX3CR1, CXCL, CXCL1, CXCL2, CXCL3, CXCL4, CXCL5,CXCL6, CXCL7, CXCL8, CXCL9, CXCL10, CXCL11, CXCL12, CXCL13, CXCL14,CXCL15, CXCL16, CXCR, CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CXCR6,cytokeratin tumor-associated antigen, DAN, DCC, DcR3, DC-SIGN, Decayaccelerating factor, des(1-3)-IGF-I (brain IGF-1), Dhh, digoxin, DNAM-1,Dnase, Dpp, DPPIV/CD26, Dtk, ECAD, EDA, EDA-A1, EDA-A2, EDAR, EGF, EGFR(ErbB-1), EMA, EMMPRIN, ENA, endothelin receptor, Enkephalinase, eNOS,Eot, eotaxin1, EpCAM, Ephrin B2/EphB4, EPO, ERCC, E-selectin, ET-1,Factor IIa, Factor VII, Factor VIIIc, Factor IX, fibroblast activationprotein (FAP), Fas, FcR1, FEN-1, Ferritin, FGF, FGF-19, FGF-2, FGF3,FGF-8, FGFR, FGFR-3, Fibrin, FL, FLIP, Flt-3, Flt-4, Folliclestimulating hormone, Fractalkine, FZD1, FZD2, FZD3, FZD4, FZD5, FZD6,FZD7, FZD8, FZD9, FZD10, G250, Gas 6, GCP-2, GCSF, GD2, GD3, GDF, GDF-1,GDF-3 (Vgr-2), GDF-5 (BMP-14, CDMP-1), GDF-6 (BMP-13, CDMP-2), GDF-7(BMP-12, CDMP-3), GDF-8 (Myostatin), GDF-9, GDF-15 (MIC-1), GDNF, GDNF,GFAP, GFRa-1, GFR-alpha1, GFR-alpha2, GFR-alpha3, GITR, Glucagon, Glut4, glycoprotein IIb/IIIa (GP IIb/IIIa), GM-CSF, gp130, gp72, GRO, Growthhormone releasing factor, Hapten (NP-cap or NIP-cap), HB-EGF, HCC, HCMVgB envelope glycoprotein, HCMV) gH envelope glycoprotein, HCMV UL,Hemopoietic growth factor (HGF), Hep B gp120, heparanase, Her2, Her2/neu(ErbB-2), Her3 (ErbB-3), Her4 (ErbB-4), herpes simplex virus (HSV) gBglycoprotein, HSV gD glycoprotein, HGFA, High molecular weightmelanoma-associated antigen (HMW-MAA), HIV gp120, HIV IIIB gp 120 V3loop, HLA, HLA-DR, HM1.24, HMFG PEM, HRG, Hrk, human cardiac myosin,human cytomegalovirus (HCMV), human growth hormone (HGH), HVEM, 1-309,IAP, ICAM, ICAM-1, ICAM-3, ICE, ICOS, IFNg, Ig, IgA receptor, IgE, IGF,IGF binding proteins, IGF-1R, IGFBP, IGF-I, IGF-II, IL, IL-1, IL-1R,IL-2, IL-2R, IL-4, IL-4R, IL-5, IL-5R, IL-6, IL-6R, IL-8, IL-9, IL-10,IL-12, IL-13, IL-15, IL-18, IL-18R, IL-23, interferon (INF)-alpha,INF-beta, INF-gamma, Inhibin, iNOS, Insulin A-chain, Insulin B-chain,Insulin-like growth factor 1, integrin alpha2, integrin alpha3, integrinalpha4, integrin alpha4/beta1, integrin alpha4/beta7, integrin alpha5(alphaV), integrin alpha5/beta1, integrin alpha5/beta3, integrin alpha6,integrin beta1, integrin beta2, interferon gamma, IP-10, I-TAC, JE,Kallikrein 2, Kallikrein 5, Kallikrein 6, Kallikrein 11, Kallikrein 12,Kallikrein 14, Kallikrein 15, Kallikrein L1, Kallikrein L2, KallikreinL3, Kallikrein L4, KC, KDR, Keratinocyte Growth Factor (KGF), laminin 5,LAMP, LAP, LAP (TGF-1), Latent TGF-1, Latent TGF-1 bp1, LBP, LDGF,LECT2, Lefty, Lewis-Y antigen, Lewis-Y related antigen, LFA-1, LFA-3,Lfo, LIF, LIGHT, lipoproteins, LIX, LKN, Lptn, L-Selectin, LT-a, LT-b,LTB4, LTBP-1, Lung surfactant, Luteinizing hormone, Lymphotoxin BetaReceptor, Mac-1, MAdCAM, MAG, MAP2, MARC, MCAM, MCAM, MCK-2, MCP, M-CSF,MDC, Mer, METALLOPROTEASES, MGDF receptor, MGMT, MHC (HLA-DR), MIF, MIG,MIP, MIP-1-alpha, MK, MMAC1, MMP, MMP-1, MMP-10, MMP-11, MMP-12, MMP-13,MMP-14, MMP-15, MMP-2, MMP-24, MMP-3, MMP-7, MMP-8, MMP-9, MPIF, Mpo,MSK, MSP, mucin (Muc1), MUC18, Muellerian-inhibitin substance, Mug,MuSK, NAIP, NAP, NCAD, N-Cadherin, NCA 90, NCAM, NCAM, Neprilysin,Neurotrophin-3, -4, or -6, Neurturin, Neuronal growth factor (NGF),NGFR, NGF-beta, nNOS, NO, NOS, Npn, NRG-3, NT, NTN, OB, OGG1, OPG, OPN,OSM, OX40L, OX40R, p150, p95, PADPr, Parathyroid hormone, PARC, PARP,PBR, PBSF, PCAD, P-Cadherin, PCNA, PDGF, PDGF, PDK-1, PECAM, PEM, PF4,PGE, PGF, PGI2, PGJ2, PIN, PLA2, placental alkaline phosphatase (PLAP),P1GF, PLP, PP14, Proinsulin, Prorelaxin, Protein C, PS, PSA, PSCA,prostate specific membrane antigen (PSMA), PTEN, PTHrp, Ptk, PTN, R51,RANK, RANKL, RANTES, RANTES, Relaxin A-chain, Relaxin B-chain, renin,respiratory syncytial virus (RSV) F, RSV Fgp, Ret, Rheumatoid factors,RLIP76, RPA2, RSK, 5100, SCF/KL, SDF-1, SERINE, Serum albumin, sFRP-3,Shh, SIGIRR, SK-1, SLAM, SLPI, SMAC, SMDF, SMOH, SOD, SPARC, Stat,STEAP, STEAP-II, TACE, TACI, TAG-72 (tumor-associated glycoprotein-72),TARC, TCA-3, T-cell receptors (e.g., T-cell receptor alpha/beta), TdT,TECK, TEM1, TEMS, TEM7, TEM8, TERT, testicular PLAP-like alkalinephosphatase, TfR, TGF, TGF-alpha, TGF-beta, TGF-beta Pan Specific,TGF-beta RI (ALK-5), TGF-beta RII, TGF-beta RIIb, TGF-beta RIII,TGF-beta1, TGF-beta2, TGF-beta3, TGF-beta4, TGF-beta5, Thrombin, ThymusCk-1, Thyroid stimulating hormone, Tie, TIMP, TIQ, Tissue Factor,TMEFF2, Tmpo, TMPRSS2, TNF, TNF-alpha, TNF-alpha beta, TNF-beta2, TNFc,TNF-RI, TNF-RII, TNFRSF10A (TRAIL R1 Apo-2, DR4), TNFRSF10B (TRAIL R2DR5, KILLER, TRICK-2A, TRICK-B), TNFRSF10C (TRAIL R3 DcR1, LIT, TRID),TNFRSF10D (TRAIL R4 DcR2, TRUNDD), TNFRSF11A (RANK ODF R, TRANCE R),TNFRSF11B (OPG OCIF, TR1), TNFRSF12 (TWEAK R FN14), TNFRSF13B (TACI),TNFRSF13C (BAFF R), TNFRSF14 (HVEM ATAR, HveA, LIGHT R, TR2), TNFRSF16(NGFR p75NTR), TNFRSF17 (BCMA), TNFRSF18 (GITR AITR), TNFRSF19 (TROYTAJ, TRADE), TNFRSF19L (RELT), TNFRSF1A (TNF RI CD120a, p55-60),TNFRSF1B (TNF RII CD120b, p75-80), TNFRSF26 (TNFRH3), TNFRSF3 (LTbR TNFRIII, TNFC R), TNFRSF4 (OX40 ACT35, TXGP1 R), TNFRSF5 (CD40 p50),TNFRSF6 (Fas Apo-1, APT1, CD95), TNFRSF6B (DcR3 M68, TR6), TNFRSF7(CD27), TNFRSF8 (CD30), TNFRSF9 (4-1BB CD137, ILA), TNFRSF21 (DR6),TNFRSF22 (DcTRAIL R2 TNFRH2), TNFRST23 (DcTRAIL R1 TNFRH1), TNFRSF25(DR3 Apo-3, LARD, TR-3, TRAMP, WSL-1), TNFSF10 (TRAIL Apo-2 Ligand,TL2), TNFSF11 (TRANCE/RANK Ligand ODF, OPG Ligand), TNFSF12 (TWEAK Apo-3Ligand, DR3 Ligand), TNFSF13 (APRIL TALL2), TNFSF13B (BAFF BLYS, TALL1,THANK, TNFSF20), TNFSF14 (LIGHT HVEM Ligand, LTg), TNFSF15 (TL1A/VEGI),TNFSF18 (GITR Ligand AITR Ligand, TL6), TNFSF1A (TNF-α Conectin, DIF,TNFSF2), TNFSF1B (TNF-b LTa, TNFSF1), TNFSF3 (LTb TNFC, p33), TNFSF4(OX40 Ligand gp34, TXGP1), TNFSF5 (CD40 Ligand CD154, gp39, HIGM1, IMD3,TRAP), TNFSF6 (Fas Ligand Apo-1 Ligand, APT1 Ligand), TNFSF7 (CD27Ligand CD70), TNFSF8 (CD30 Ligand CD153), TNFSF9 (4-1BB Ligand CD137Ligand), TP-1, t-PA, Tpo, TRAIL, TRAIL R, TRAIL-R1, TRAIL-R2, TRANCE,transferring receptor, TRF, Trk, TROP-2, TSG, TSLP, tumor-associatedantigen CA 125, tumor-associated antigen expressing Lewis Y relatedcarbohydrate, TWEAK, TXB2, Ung, uPAR, uPAR-1, Urokinase, VCAM, VCAM-1,VECAD, VE-Cadherin, VE-cadherin-2, VEFGR-1 (flt-1), VEGF, VEGFR, VEGFR-3(flt-4), VEGI, VIM, Viral antigens, VLA, VLA-1, VLA-4, VNR integrin, vonWillebrands factor, WIF-1, WNT1, WNT2, WNT2B/13, WNT3, WNT3A, WNT4,WNTSA, WNTSB, WNT6, WNT7A, WNT7B, WNT8A, WNT8B, WNT9A, WNT9A, WNT9B,WNT10A, WNT10B, WNT11, WNT16, XCL1, XCL2, XCR1, XCR1, XEDAR, XIAP, XPD,and receptors for hormones and growth factors.

Exemplary antigens that may be targeted specifically by theimmunoglobulins of the invention include but are not limited to: CD20,CD19, Her2, EGFR, EpCAM, CD3, FcγRIIIa (CD16), FcγRIIa (CD32a), FcγRIIb(CD32b), FcγRI (CD64), Toll-like receptors (TLRs) such as TLR4 and TLR9,cytokines such as IL-2, IL-5, IL-13, IL-12, IL-23, and TNFα, cytokinereceptors such as IL-2R, chemokines, chemokine receptors, growth factorssuch as VEGF and HGF, and the like. To form the bispecific antibodies ofthe invention, antibodies to any combination of these antigens can bemade; that is, each of these antigens can be optionally andindependently included or excluded from a bispecific antibody accordingto the present invention.

Particularly preferred combinations for bispecific antibodies are anantigen-binding domain to CD3 and an antigen binding domain selectedfrom a domain that binds CD19, CD20, CD38 and CD123, the sequences ofwhich are shown in the Figures.

Nucleic Acids of the Invention

The invention further provides nucleic acid compositions encoding thebispecific antibodies of the invention. As will be appreciated by thosein the art, the nucleic acid compositions will depend on the format andscaffold of the heterodimeric protein. Thus, for example, when theformat requires three amino acid sequences, such as for the triple Fformat (e.g. a first amino acid monomer comprising an Fc domain and ascFv, a second amino acid monomer comprising a heavy chain and a lightchain), three nucleic acid sequences can be incorporated into one ormore expression vectors for expression. Similarly, some formats (e.g.dual scFv formats such as disclosed in FIG. 1) only two nucleic acidsare needed; again, they can be put into one or two expression vectors.

As is known in the art, the nucleic acids encoding the components of theinvention can be incorporated into expression vectors as is known in theart, and depending on the host cells used to produce the heterodimericantibodies of the invention. Generally the nucleic acids are operablylinked to any number of regulatory elements (promoters, origin ofreplication, selectable markers, ribosomal binding sites, inducers,etc.). The expression vectors can be extra-chromosomal or integratingvectors.

The nucleic acids and/or expression vectors of the invention are thentransformed into any number of different types of host cells as is wellknown in the art, including mammalian, bacterial, yeast, insect and/orfungal cells, with mammalian cells (e.g. CHO cells), finding use in manyembodiments.

In some embodiments, nucleic acids encoding each monomer and theoptional nucleic acid encoding a light chain, as applicable depending onthe format, are each contained within a single expression vector,generally under different or the same promoter controls. In embodimentsof particular use in the present invention, each of these two or threenucleic acids are contained on a different expression vector. As shownherein and in 62/025,931, hereby incorporated by reference, differentvector ratios can be used to drive heterodimer formation. That is,surprisingly, while the proteins comprise first monomer:secondmonomer:light chains (in the case of many of the embodiments herein thathave three polypeptides comprising the heterodimeric antibody) in a1:1:2 ratio, these are not the ratios that give the best results.

The heterodimeric antibodies of the invention are made by culturing hostcells comprising the expression vector(s) as is well known in the art.Once produced, traditional antibody purification steps are done,including an ion exchange chromotography step. As discussed herein,having the pIs of the two monomers differ by at least 0.5 can allowseparation by ion exchange chromatography or isoelectric focusing, orother methods sensitive to isoelectric point. That is, the inclusion ofpI substitutions that alter the isoelectric point (pI) of each monomerso that such that each monomer has a different pI and the heterodimeralso has a distinct pI, thus facilitating isoelectric purification ofthe “triple F” heterodimer (e.g., anionic exchange columns, cationicexchange columns). These substitutions also aid in the determination andmonitoring of any contaminating dual scFv-Fc and mAb homodimerspost-purification (e.g., IEF gels, cIEF, and analytical IEX columns).

Treatments

Once made, the compositions of the invention find use in a number ofapplications. CD20, CD38 and CD123 are all unregulated in manyhematopoeitic malignancies and in cell lines derived from varioushematopoietic malignancies, accordingly, the heterodimeric antibodies ofthe invention find use in treating cancer, including but not limited to,all B cell lymphomas and leukemias, including but not limited tonon-Hodgkin's lymphoma (NHL), Burkitt's lymphoma (BL), multiple myeloma(MM), B chronic lymphocytic leukemia (B-CLL), B and T acute lymphocyticleukemia (ALL), T cell lymphoma (TCL), acute myeloid leukemia (AML),hairy cell leukemia (HCL), Hodgkin's Lymphoma (HL), chronic lymphocyticleukemia (CLL), non-Hodgkin's lymphoma, and chronic myeloid leukemia(CML).

Accordingly, the heterodimeric compositions of the invention find use inthe treatment of these cancers.

Antibody Compositions for In Vivo Administration

Formulations of the antibodies used in accordance with the presentinvention are prepared for storage by mixing an antibody having thedesired degree of purity with optional pharmaceutically acceptablecarriers, excipients or stabilizers (Remington's Pharmaceutical Sciences16th edition, Osol, A. Ed. [1980]), in the form of lyophilizedformulations or aqueous solutions. Acceptable carriers, excipients, orstabilizers are nontoxic to recipients at the dosages and concentrationsemployed, and include buffers such as phosphate, citrate, and otherorganic acids; antioxidants including ascorbic acid and methionine;preservatives (such as octadecyldimethylbenzyl ammonium chloride;hexamethonium chloride; benzalkonium chloride, benzethonium chloride;phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propylparaben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol);low molecular weight (less than about 10 residues) polypeptides;proteins, such as serum albumin, gelatin, or immunoglobulins;hydrophilic polymers such as polyvinylpyrrolidone; amino acids such asglycine, glutamine, asparagine, histidine, arginine, or lysine;monosaccharides, disaccharides, and other carbohydrates includingglucose, mannose, or dextrins; chelating agents such as EDTA; sugarssuch as sucrose, mannitol, trehalose or sorbitol; salt-formingcounter-ions such as sodium; metal complexes (e.g. Zn-proteincomplexes); and/or non-ionic surfactants such as TWEEN™, PLURONICS™ orpolyethylene glycol (PEG).

The formulation herein may also contain more than one active compound asnecessary for the particular indication being treated, preferably thosewith complementary activities that do not adversely affect each other.For example, it may be desirable to provide antibodies with otherspecificities. Alternatively, or in addition, the composition maycomprise a cytotoxic agent, cytokine, growth inhibitory agent and/orsmall molecule antagonist. Such molecules are suitably present incombination in amounts that are effective for the purpose intended.

The active ingredients may also be entrapped in microcapsules prepared,for example, by coacervation techniques or by interfacialpolymerization, for example, hydroxymethylcellulose orgelatin-microcapsules and poly-(methylmethacylate) microcapsules,respectively, in colloidal drug delivery systems (for example,liposomes, albumin microspheres, microemulsions, nano-particles andnanocapsules) or in macroemulsions. Such techniques are disclosed inRemington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980).

The formulations to be used for in vivo administration should besterile, or nearly so. This is readily accomplished by filtrationthrough sterile filtration membranes.

Sustained-release preparations may be prepared. Suitable examples ofsustained-release preparations include semipermeable matrices of solidhydrophobic polymers containing the antibody, which matrices are in theform of shaped articles, e.g. films, or microcapsules. Examples ofsustained-release matrices include polyesters, hydrogels (for example,poly(2-hydroxyethyl-methacrylate), or poly(vinylalcohol)), polylactides(U.S. Pat. No. 3,773,919), copolymers of L-glutamic acid and .gamma.ethyl-L-glutamate, non-degradable ethylene-vinyl acetate, degradablelactic acid-glycolic acid copolymers such as the LUPRON DEPOT™(injectable microspheres composed of lactic acid-glycolic acid copolymerand leuprolide acetate), and poly-D-(−)-3-hydroxybutyric acid. Whilepolymers such as ethylene-vinyl acetate and lactic acid-glycolic acidenable release of molecules for over 100 days, certain hydrogels releaseproteins for shorter time periods.

When encapsulated antibodies remain in the body for a long time, theymay denature or aggregate as a result of exposure to moisture at 37° C.,resulting in a loss of biological activity and possible changes inimmunogenicity. Rational strategies can be devised for stabilizationdepending on the mechanism involved. For example, if the aggregationmechanism is discovered to be intermolecular S—S bond formation throughthio-disulfide interchange, stabilization may be achieved by modifyingsulfhydryl residues, lyophilizing from acidic solutions, controllingmoisture content, using appropriate additives, and developing specificpolymer matrix compositions.

Administrative Modalities

The antibodies and chemotherapeutic agents of the invention areadministered to a subject, in accord with known methods, such asintravenous administration as a bolus or by continuous infusion over aperiod of time, by intramuscular, intraperitoneal, intracerobrospinal,subcutaneous, intra-articular, intrasynovial, intrathecal, oral,topical, or inhalation routes. Intravenous or subcutaneousadministration of the antibody is preferred.

Treatment Modalities

In the methods of the invention, therapy is used to provide a positivetherapeutic response with respect to a disease or condition. By“positive therapeutic response” is intended an improvement in thedisease or condition, and/or an improvement in the symptoms associatedwith the disease or condition. For example, a positive therapeuticresponse would refer to one or more of the following improvements in thedisease: (1) a reduction in the number of neoplastic cells; (2) anincrease in neoplastic cell death; (3) inhibition of neoplastic cellsurvival; (5) inhibition (i.e., slowing to some extent, preferablyhalting) of tumor growth; (6) an increased patient survival rate; and(7) some relief from one or more symptoms associated with the disease orcondition.

Positive therapeutic responses in any given disease or condition can bedetermined by standardized response criteria specific to that disease orcondition. Tumor response can be assessed for changes in tumormorphology (i.e., overall tumor burden, tumor size, and the like) usingscreening techniques such as magnetic resonance imaging (MRI) scan,x-radiographic imaging, computed tomographic (CT) scan, bone scanimaging, endoscopy, and tumor biopsy sampling including bone marrowaspiration (BMA) and counting of tumor cells in the circulation.

In addition to these positive therapeutic responses, the subjectundergoing therapy may experience the beneficial effect of animprovement in the symptoms associated with the disease.

An improvement in the disease may be characterized as a completeresponse. By “complete response” is intended an absence of clinicallydetectable disease with normalization of any previously abnormalradiographic studies, bone marrow, and cerebrospinal fluid (CSF) orabnormal monoclonal protein in the case of myeloma.

Such a response may persist for at least 4 to 8 weeks, or sometimes 6 to8 weeks, following treatment according to the methods of the invention.Alternatively, an improvement in the disease may be categorized as beinga partial response. By “partial response” is intended at least about a50% decrease in all measurable tumor burden (i.e., the number ofmalignant cells present in the subject, or the measured bulk of tumormasses or the quantity of abnormal monoclonal protein) in the absence ofnew lesions, which may persist for 4 to 8 weeks, or 6 to 8 weeks.

Treatment according to the present invention includes a “therapeuticallyeffective amount” of the medicaments used. A “therapeutically effectiveamount” refers to an amount effective, at dosages and for periods oftime necessary, to achieve a desired therapeutic result.

A therapeutically effective amount may vary according to factors such asthe disease state, age, sex, and weight of the individual, and theability of the medicaments to elicit a desired response in theindividual. A therapeutically effective amount is also one in which anytoxic or detrimental effects of the antibody or antibody portion areoutweighed by the therapeutically beneficial effects.

A “therapeutically effective amount” for tumor therapy may also bemeasured by its ability to stabilize the progression of disease. Theability of a compound to inhibit cancer may be evaluated in an animalmodel system predictive of efficacy in human tumors.

Alternatively, this property of a composition may be evaluated byexamining the ability of the compound to inhibit cell growth or toinduce apoptosis by in vitro assays known to the skilled practitioner. Atherapeutically effective amount of a therapeutic compound may decreasetumor size, or otherwise ameliorate symptoms in a subject. One ofordinary skill in the art would be able to determine such amounts basedon such factors as the subject's size, the severity of the subject'ssymptoms, and the particular composition or route of administrationselected.

Dosage regimens are adjusted to provide the optimum desired response(e.g., a therapeutic response). For example, a single bolus may beadministered, several divided doses may be administered over time or thedose may be proportionally reduced or increased as indicated by theexigencies of the therapeutic situation. Parenteral compositions may beformulated in dosage unit form for ease of administration and uniformityof dosage. Dosage unit form as used herein refers to physically discreteunits suited as unitary dosages for the subjects to be treated; eachunit contains a predetermined quantity of active compound calculated toproduce the desired therapeutic effect in association with the requiredpharmaceutical carrier.

The specification for the dosage unit forms of the present invention aredictated by and directly dependent on (a) the unique characteristics ofthe active compound and the particular therapeutic effect to beachieved, and (b) the limitations inherent in the art of compoundingsuch an active compound for the treatment of sensitivity in individuals.

The efficient dosages and the dosage regimens for the bispecificantibodies used in the present invention depend on the disease orcondition to be treated and may be determined by the persons skilled inthe art.

An exemplary, non-limiting range for a therapeutically effective amountof an bispecific antibody used in the present invention is about 0.1-100mg/kg, such as about 0.1-50 mg/kg, for example about 0.1-20 mg/kg, suchas about 0.1-10 mg/kg, for instance about 0.5, about such as 0.3, about1, or about 3 mg/kg. In another embodiment, the antibody is administeredin a dose of 1 mg/kg or more, such as a dose of from 1 to 20 mg/kg, e.g.a dose of from 5 to 20 mg/kg, e.g. a dose of 8 mg/kg.

A medical professional having ordinary skill in the art may readilydetermine and prescribe the effective amount of the pharmaceuticalcomposition required. For example, a physician or a veterinarian couldstart doses of the medicament employed in the pharmaceutical compositionat levels lower than that required in order to achieve the desiredtherapeutic effect and gradually increase the dosage until the desiredeffect is achieved.

In one embodiment, the bispecific antibody is administered by infusionin a weekly dosage of from 10 to 500 mg/kg such as of from 200 to 400mg/kg Such administration may be repeated, e.g., 1 to 8 times, such as 3to 5 times. The administration may be performed by continuous infusionover a period of from 2 to 24 hours, such as of from 2 to 12 hours.

In one embodiment, the bispecific antibody is administered by slowcontinuous infusion over a long period, such as more than 24 hours, ifrequired to reduce side effects including toxicity.

In one embodiment the bispecific antibody is administered in a weeklydosage of from 250 mg to 2000 mg, such as for example 300 mg, 500 mg,700 mg, 1000 mg, 1500 mg or 2000 mg, for up to 8 times, such as from 4to 6 times. The administration may be performed by continuous infusionover a period of from 2 to 24 hours, such as of from 2 to 12 hours. Suchregimen may be repeated one or more times as necessary, for example,after 6 months or 12 months. The dosage may be determined or adjusted bymeasuring the amount of compound of the present invention in the bloodupon administration by for instance taking out a biological sample andusing anti-idiotypic antibodies which target the antigen binding regionof the bispecific antibody.

In a further embodiment, the bispecific antibody is administered onceweekly for 2 to 12 weeks, such as for 3 to 10 weeks, such as for 4 to 8weeks.

In one embodiment, the bispecific antibody is administered bymaintenance therapy, such as, e.g., once a week for a period of 6 monthsor more.

In one embodiment, the bispecific antibody is administered by a regimenincluding one infusion of an bispecific antibody followed by an infusionof an bispecific antibody conjugated to a radioisotope. The regimen maybe repeated, e.g., 7 to 9 days later.

As non-limiting examples, treatment according to the present inventionmay be provided as a daily dosage of an antibody in an amount of about0.1-100 mg/kg, such as 0.5, 0.9, 1.0, 1.1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,28, 29, 30, 40, 45, 50, 60, 70, 80, 90 or 100 mg/kg, per day, on atleast one of day 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,35, 36, 37, 38, 39, or 40, or alternatively, at least one of week 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 afterinitiation of treatment, or any combination thereof, using single ordivided doses of every 24, 12, 8, 6, 4, or 2 hours, or any combinationthereof.

In some embodiments the bispecific antibody molecule thereof is used incombination with one or more additional therapeutic agents, e.g. achemotherapeutic agent. Non-limiting examples of DNA damagingchemotherapeutic agents include topoisomerase I inhibitors (e.g.,irinotecan, topotecan, camptothecin and analogs or metabolites thereof,and doxorubicin); topoisomerase II inhibitors (e.g., etoposide,teniposide, and daunorubicin); alkylating agents (e.g., melphalan,chlorambucil, busulfan, thiotepa, ifosfamide, carmustine, lomustine,semustine, streptozocin, decarbazine, methotrexate, mitomycin C, andcyclophosphamide); DNA intercalators (e.g., cisplatin, oxaliplatin, andcarboplatin); DNA intercalators and free radical generators such asbleomycin; and nucleoside mimetics (e.g., 5-fluorouracil, capecitibine,gemcitabine, fludarabine, cytarabine, mercaptopurine, thioguanine,pentostatin, and hydroxyurea).

Chemotherapeutic agents that disrupt cell replication include:paclitaxel, docetaxel, and related analogs; vincristine, vinblastin, andrelated analogs; thalidomide, lenalidomide, and related analogs (e.g.,CC-5013 and CC-4047); protein tyrosine kinase inhibitors (e.g., imatinibmesylate and gefitinib); proteasome inhibitors (e.g., bortezomib); NF-κBinhibitors, including inhibitors of IκB kinase; antibodies which bind toproteins overexpressed in cancers and thereby downregulate cellreplication (e.g., trastuzumab, rituximab, cetuximab, and bevacizumab);and other inhibitors of proteins or enzymes known to be upregulated,over-expressed or activated in cancers, the inhibition of whichdownregulates cell replication.

In some embodiments, the antibodies of the invention can be used priorto, concurrent with, or after treatment with Velcade® (bortezomib).

All cited references are herein expressly incorporated by reference intheir entirety.

Whereas particular embodiments of the invention have been describedabove for purposes of illustration, it will be appreciated by thoseskilled in the art that numerous variations of the details may be madewithout departing from the invention as described in the appendedclaims.

EXAMPLES

Examples are provided below to illustrate the present invention. Theseexamples are not meant to constrain the present invention to anyparticular application or theory of operation. For all constant regionpositions discussed in the present invention, numbering is according tothe EU index as in Kabat (Kabat et al., 1991, Sequences of Proteins ofImmunological Interest, 5th Ed., United States Public Health Service,National Institutes of Health, Bethesda, entirely incorporated byreference). Those skilled in the art of antibodies will appreciate thatthis convention consists of nonsequential numbering in specific regionsof an immunoglobulin sequence, enabling a normalized reference toconserved positions in immunoglobulin families. Accordingly, thepositions of any given immunoglobulin as defined by the EU index willnot necessarily correspond to its sequential sequence.

General and specific scientific techniques are outlined in USPublications 2015/0307629, 2014/0288275 and WO2014/145806, all of whichare expressly incorporated by reference in their entirety andparticularly for the techniques outlined therein.

EXAMPLES Example 1: Alternate Formats

Bispecifics Production

Cartoon schematics of anti-CD38×anti-CD3 bispecifics are shown inFIG. 1. Amino acid sequences for alternate format anti-CD38×anti-CD3bispecifics are listed in FIG. 39 to FIG. 43. DNA encoding the threechains needed for bispecific expression were generated by gene synthesis(Blue Heron Biotechnology, Bothell, Wash.) and were subcloned usingstandard molecular biology techniques into the expression vector pTT5.Substitutions were introduced using either site-directed mutagenesis(QuikChange, Stratagene, Cedar Creek, Tex.) or additional gene synthesisand subcloning. DNA was transfected into HEK293E cells for expressionand resulting proteins were purified from the supernatant using proteinA affinity (GE Healthcare) and cation exchange chromatography. Yieldsfollowing protein A affinity purification are shown in FIG. 35. Cationexchange chromatography purification was performed using a HiTrap SP HPcolumn (GE Healthcare) with a wash/equilibration buffer of 50 mM MES, pH6.0 and an elution buffer of 50 mM MES, pH 6.0+1 M NaCl linear gradient(see FIG. 36 for chromatograms).

Redirected T Cell Cytotoxicity

Anti-CD38×anti-CD3 bispecifics were characterized in vitro forredirected T cell cytotoxicity (RTCC) of the CD38⁺ RPMI8266 myeloma cellline. 10 k RPMI8266 cells were incubated for 24 h with 500 k humanPBMCs. RTCC was measured by LDH fluorescence as indicated (see FIG. 37).

Example 2

Redirected T Cell Cytotoxicity

Anti-CD38×anti-CD3 Fab-scFv-Fc bispecifics were characterized in vitrofor redirected T cell cytotoxicity (RTCC) of the CD38+ RPMI8266 myelomacell line. 40 k RPMI8266 cells were incubated for 96 h with 400 k humanPBMCs. RTCC was measured by flow cytometry as indicated (see FIG. 44).CD4+ and CD8+ T cell expression of CD69, Ki-67, and PI-9 were alsocharacterized by flow cytometry and are shown in FIG. 45.

Mouse Model of Anti-Tumor Activity

Four groups of five NOD scid gamma (NSG) mice each were engrafted with5×106 RPMI8226TrS tumor cells (multiple myeloma, luciferase-expressing)by intravenous tail vein injection on Day −23. On Day 0, mice wereengrafted intraperitoneally with 10×106 human PBMCs. After PBMCengraftment on Day 0, test articles are dosed weekly (Days 0, 7) byintraperitoneal injection at dose levels indicated in FIG. 4. Studydesign is further summarized in FIG. 46. Tumor growth was monitored bymeasuring total flux per mouse using an in vivo imaging system (IVIS®).Both XmAb13551 and XmAb15426 showed substantial anti-tumor effects (seeFIG. 47 and FIG. 48).

Studies in Cynomolgus Monkey

Cynomolgus monkeys were given a single dose of anti-CD38×anti-CD3bispecifics. An anti-RSV×anti-CD3 bispecific control was also included.Dose levels were: 20 μg/kg XmAb13551 (n=2), 0.5 mg/kg XmAb15426 (n=3), 3mg/kg XmAb14702 (n=3), or 3 mg/kg XmAb13245 (anti-RSV×anti-CD3 control,n=3) (in 3 independent studies). Anti-CD38×anti-CD3 bispecifics rapidlydepleted CD38+ cells in peripheral blood (see FIG. 49).Anti-CD38×anti-CD3 bispecifics resulted in T cell activation as measuredby CD69 expression (see FIG. 50). Serum levels of IL-6 were alsomeasured (see FIG. 51). Note that, compared to XmAb13551, XmAb15426 hadan increased duration of CD38+ cell depletion and lower levels of T cellactivation and IL-6 production.

XmAb15426 and XmAb14702 were tested at single doses of 0.5 mg/kg and 3mg/kg respectively. Both antibodies were well-tolerated at these higherdoses, consistent with the moderate levels of IL6 observed in serum fromthe treated monkeys. Moreover, XmAb15426, with intermediate CD3affinity, more effectively depleted CD38+ cells at 0.5 mg/kg compared tothe original high-affinity XmAb13551 dosed at 2, 5 or 20 μg/kg.Depletion by XmAb15426 was more sustained compared to the highest doseof XmAb13551 in the previous study (7 vs. 2 days, respectively).Notably, although target cell depletion was greater for XmAb15426, Tcell activation (CD69, CD25 and PD1 induction) was much lower in monkeystreated with XmAb15426 even dosed 25-fold higher than the 20 μg/kgXmAb13551 group. XmAb14702, with very low CD3 affinity, had littleeffeft on CD38+ cells and T cell activation.

These results demonstrate that modulating T cell activation byattenuating CD3 affinity is a promising method to improve thetherapeutic window of T cell-engaging bispecific antibodies. Thisstrategy has potential to expand the set of antigens amenable totargeted T cell immunotherapy by improving tolerability and enablinghigher dosing to overcome antigen sink clearance with targets such asCD38. We have shown that by reducing affinity for CD3, XmAb 15426effectively depletes CD38+ cells while minimizing the CRS effects seenwith comparable doses of its high-affinity counterpart XmAb13551.

Example 3

CDR Development for CD123

The starting point for CDR development for a humanized antibody Fabhuman CD123 was the 7G3 murine antibody variable and light regions,referred to herein as “7G3 H0L0”, from ATCC HB-12009. However, theinitial humanization (H1_L1; sequence shown in FIG. 136) resulted in asignificant loss of affinity (5 to 10 fold affinity, as shown in FIGS.156B and C). This loss of affinity was mostly due to the heavy chainhumanization, as shown for the H1_L0 construct (e.g. the first humanizedheavy chain with the murine light chain), with the H1_L1 constructshowing the full loss of 10-fold. This was consistent with the 10 foldloss in RTCC (redirected T cell cytotoxicity) potency, as shown in FIG.156D, when tested against KG1a cells, which express CD123.

Accordingly, two rounds of affinity/stabilization optimization were run.The first round (“library 1” as shown in FIG. 157), was the generationof 108 variants, including LDA, targeted and reversion substitutions,that were then affinity screened in a Fab format (humanized variableheavy domain fused to a human CH1 from IgG1) on a CD123 chip, with thestability of neutral and higher affinity variants screened on DSF.

As shown in FIG. 158, the Tm of the original H1L1 variant was increasedas compared to the starting H0L0, with the results of additionalvariants in the H1L1 parent being also shown in FIG. 158.

Round 1 variants were then built into a bottle opener format as furtheroutlined herein, using a scFv to CD3 and the Fab as developed, and thentested in a KG-1a binding assay as well as an RTCC assay as shown inFIG. 159. While the first round of optimization improved the affinityand efficacy of the variants, additional optimization was required.

The second round, “Round 2”, as shown in FIG. 160, resulted in thereturn of binding affinity to the murine levels of H0L0 as well as thereturn of the RTCC activity. The best variant, XENP14045 had improvedaffinity as compared to both the first humanization sequence (H1L1;showing +21-fold improvement over H1L1), as well as a two-fold increasein activity over the parental murine antibody (7G3; H0L0). It should benoted that XENP13967 is the equivalent to XENP14045 on the CD123 side;13967 has a different CD3 scFv as shown in the sequences.

The round 2 optimization also resulted in an increase in stability asmeasured by Tm. FIG. 161 shows the results of the Tm assay, with a +5Cimprovement of XENP13967 (and correspondingly XENP14045) over theoriginal chimeric (e.g. variable heavy and light murine sequences) and a+4C as compared to the original H1L1 variant. 13967/14045 has 11substitutions as compared to the original H1L1 sequence). In addition,during the second round, a potential deamindation site (−NS motif) wasremoved from the light chain CDR1.

Example 4

CDR Development for CD20

Two anti-CD20 Fabs were explored in the context of the CD20×CD3bispecific format for binding affinity and efficacy. Both the XENP13677and XENP13676 are based on rituximab. The 13677 variant displayssignificantly enhanced potency relative to the 13676 variant, whose CD20affinity approximates that of the parental rituximab antibody. Bothbispecific antibodies were dosed in a cynomolgus monkey study to comparetheir in vivo properties. However, because of the higher potency of the13677 variant, it was dosed at a 10-fold lower dose of 0.03 mg/kg vs the0.3 mg/kg dosed for the lower potency 13676. At these doses, bothantibodies significantly depleted monkey B cells. However, surprisingly,the significantly more potent 13677 actually showed more rapid recoveryof the B cells at its lower dose. On the other hand, both antibodiescaused approximately the same amount of IL6 release. In conclusion, thelower affinity variant 13676 unexpectedly displays a more favorabletherapeutic profile, causing a more prolonged depletion of B cells whilemaintaining similar levels of IL6.

What is claimed:
 1. A composition comprising an CD123 antigen bindingdomain comprising: a) a variable heavy domain comprising a vhCDR1 havingSEQ ID NO:440, vhCDR2 having SEQ ID NO:441 and a vhCDR3 having SEQ IDNO:442; and b) a variable light domain comprising a v1CDR1 having SEQ IDNO:444, v1CDR2 having SEQ ID NO:445 and a v1CDR3 having SEQ ID NO:446.2. A composition according to claim 1, wherein said variable heavydomain has an amino acid sequence according to SEQ ID NO:439 and saidvariable light domain has an amino acid sequence according to SEQ IDNO:443.
 3. A heterodimeric antibody comprising: a) a first monomercomprising: i) a first IgG Fc domain; and ii) a single chain variablefragment comprising a first variable heavy chain, a first variable lightchain, and a linker that attaches said first variable heavy chain withsaid first variable light chain; b) a second monomer comprising: i) aVH-CH1-hinge-CH2-CH3 monomer, wherein VH is a second variable heavychain comprising a vhCDR1 having SEQ ID NO:440, vhCDR2 having SEQ IDNO:441 and a vhCDR3 having SEQ ID NO:442, and CH2-CH3 is a second IgG Fcdomain; and c) a light chain comprising a second variable light chaincomprising a v1CDR1 having SEQ ID NO:444, v1CDR2 having SEQ ID NO:445and a v1CDR3 having SEQ ID NO:446, wherein said second variable heavychain and said second variable light chain form a CD123 binding domain.4. A heterodimeric antibody according to claim 3, wherein said secondvariable heavy chain has an amino acid sequence having SEQ ID NO: 439and said second variable light chain has an amino acid sequence havingSEQ ID NO:
 443. 5. A nucleic acid composition comprising: a) a nucleicacid encoding the variable heavy domain of claim 1; and b) a nucleicacid encoding the variable light domain of claim
 1. 6. An expressionvector composition comprising: a) a first expression vector comprising afirst nucleic acid encoding said variable heavy domain of claim 1; andb) a second expression vector comprising a second nucleic acid encodingsaid variable light domain of claim
 1. 7. A host cell comprising saidexpression vector composition of claim
 6. 8. A nucleic acid compositioncomprising: a) a first nucleic acid encoding said first monomer of claim3; b) a second nucleic acid encoding said second monomer chain of claim3; and c) a third nucleic acid encoding said light chain of claim
 3. 9.An expression vector composition comprising: a) a first expressionvector comprising a first nucleic acid encoding said first monomer ofclaim 3; b) a second expression vector comprising a second nucleic acidencoding said second monomer chain of claim 3; and c) a third expressionvector comprising a third nucleic acid encoding said light chain ofclaim
 3. 10. A host cell comprising said expression vector compositionof claim
 9. 11. A method of making a heterodimeric antibody according toclaim 3 comprising culturing the host cell according to claim 10 underconditions wherein said heterodimeric antibody is expressed, andrecovering said heterodimeric antibody.